Transparent film for display substrate, display substrate using the film and method of manufacturing the same, liquid crystal display, organic electroluminescence display, and touch panel

ABSTRACT

A transparent film for display substrate containing a cellulose ester, a plasticizer content in an amount of less than 1 percent, the aformentioned film being drawn 3 through 100 percent both in the direction of conveyance and across the width.

FIELD OF THE INVENTION

The present invention relates to a transparent film for displaysubstrate characterized by a low coefficient of linear expansion andpreferable application to a display substrate, and the manufacturingmethod thereof, particularly to a liquid crystal display, organicelectroluminescence display and touch panel wherein this transparentfilm for display substrate is used as a substrate.

TECHNICAL BACKGROUND

Since glass has an excellent thermal stability and transparency as wellas low vapor permeability, the glass have been used in the prior art asa substrate for the electronic display device such as a liquid crystaldisplay device, organic electroluminescence (EL) display device, plasmadisplay device and electronic paper, as a substrate for anelectron-optical device such as a CCD or CMOS sensor, or a substrate fora solar battery. However, with the recent spread of a cellular phone andportable information terminal, there is an active demand for a substratecharacterized by flexibility, light weight and resistance to cracks, totake place of the glass as a substrate which is comparatively heavy andsusceptible to cracks.

In the liquid crystal display, birefringence is used for on-offoperation of the display, and therefore, reduced birefringence isessential. Further, when various forms of functional thin film areformed on a plastic substrate, it is exposed to high temperature. Thisrequires a high degree of resistance to heat. Especially when thetransparent conductive film that is an essential functional thin film asa display substrate is to be formed into a low-resistant crystallinethin film, it is required to have a resistance to a high temperature of180 degrees Celsius. Since all of these three physical properties areindispensable, it can be easily seen that many of the plastic substratesare not suited for display.

The material for the plastic substrate meeting such requirements isexemplified by polyether sulfone and polycarbonate. Especially, theOfficial Gazette of Japanese Patent Tokkaihei 5-142525 discloses atransparent film formed by lamination of a polyether sulfone and acrylbased substrates, and recommends it to be used as a plastic substrate.As a result, this transparent film has come to be used in some cases.However, when the plastic substrate is used to manufacture a liquidcrystal display and an organic electroluminescence display, it has beenfound out that such a product is accompanied by various faults that havenot been observed in the glass substrate.

In the first place, unlike the glass substrate, the plastic substratehas the disadvantage of more or less allowing the passage of a gas suchas vapor and oxygen that have an adverse effect on the devicesconstituting the display.

To overcome such disadvantages, an inorganic thin film having excellentgas barrier characteristics is used to cover the plastic substrateaccording to the vacuum deposition and sputtering method. It has beenclarified that moisture permeability of the plastic substrate can bereduced by silicon oxide, for example.

However, the plastic substrate has a coefficient of thermal expansion asingle to double digit greater than the glass substrate. This hasresulted in a crack of a functional thin film arranged on the plasticsubstrate, or displacement of the pixel. It has been made clear thatsuch a problem arises. In the aforementioned gas barrier type inorganicthin film, moisture permeability is drastically increased if a crackoccurs. In the transparent conductive film, conductivity is reduced.

It is commonly known that the expansion coefficient of plastic filmrelative to heat and humidity can be reduced by drawing. Since drawingalso increases the birefringence, a plastic substrate suited for use inthe display cannot have been obtained even by drawing the aforementionedPES.

Thus, there has been no success in finding out a transparent plasticsubstrate having a low coefficient of thermal expansion in addition tothree physical properties including low birefringence, high heatresistance and high transparency.

Further, a method of providing a gas barrier layer to control thepassage of moisture or oxygen normally includes vacuum deposition,sputtering and vacuum plasma CVD methods. These methods involve use ofcomplicated and bulky equipment, and have been characterized by lowproductivity and high cost in the arrangement of an inorganic thin film.

The first object of the present invention is to provide a transparentplastic film for use in a liquid crystal display, organicelectroluminescence display or touch panel, the transparent plastic filmbeing characterized by a high degree of transparency and heatresistance, as well as reduced birefringence and coefficient of thermalexpansion.

The second object of the present invention is to provide measures forproviding a gas barrier film of low moisture permeability and highdurability by means of a simple process.

The third object of the present invention is to provide a liquid crystaldisplay and a touch panel ensuring the minimum image distortion or colormisregistration, and an organic electroluminescence displaycharacterized by a high luminance of light emission.

DISCLOSURE OF THE INVENTION

To solve the aforementioned problems, the present inventors paidattention to a cellulose ester film. The cellulose ester film is aplastic of low birefringence and high transparency, and is commonly usedas a film for protecting a polarizer in a liquid crystal displayutilizing such properties.

However, cellulose ester is a moisture absorbing resin and has adisadvantage of having a high moisture absorbing expansion coefficient.To make up for this defect of the cellulose ester, as much as 5 through20 percent by mass of such a plasticizer as a phosphoric acid ester isused in the prior art. However, it has been found out that theplasticizer reduces the glass-transition temperature of the celluloseester and increases the thermal expansion coefficient.

In an effort to solve the aforementioned problems, the inventors of thepresent invention have found out that a high glass-transitiontemperature can be achieved by keeping the percentage of plasticizercontent down below a predetermined level, and at the same time, thethermal expansion coefficient can be reduced by biaxially drawing of thecellulose ester film. Further, surprisingly, it has been found out thatcellulose ester is excellent controllability of birefringence; thebirefringence can be kept small even if the cellulose ester is drawn.The disadvantage of reduced amount of the plasticizer to be added can bereduced by formation of a gas barrier. These findings have led to thepresent invention.

The aforementioned objects of the present invention can be achieved bythe following:

-   1. A transparent film for display substrate containing a cellulose    ester and a plasticizer in an amount of less than 1 percent, the    film drawn 3 through 100 percent both in a conveyance direction and    a width direction.-   2. The transparent film for display substrate of the aforementioned    1 containing a hydrolyzed polycondensate of the cellulose ester and    an alkoxysilane expressed by the following general formula (1):    R_(4-n)Si(OR′)_(n)   General formula (1)

(where R and R′ represent a hydrogen atom or monovalent substituent, and“n” denotes 3 or 4).

-   3. The transparent film for display substrate of The aforementioned    2, wherein the hydrolyzed polycondensate of the cellulose ester and    the alkoxysilane expressed by the following general formula (1) are    expressed by the following general formula (2), and a total amount    of inorganic high molecular compounds expressed by the following    general formula (2) is less than 40 percent by mass in the    transparent film:    R_(4-n)SiO_(n/2)   General formula (2)

(where R is synonymous with that in said general formula (1)).

-   4. The transparent film for display substrate in any one of the    aforementioned 1 through 3 containing an organic crosslinking agent    having a plurality of any of the isocyanate group, thioisocyanate    group and acid hydride residue, in an amount of 1 through 20 percent    by mass, so that crosslinked with cellulose ester is formed.-   5. The transparent film for display substrate in any one of The    aforementioned 1 through 4, wherein the number average molecular    mass of the cellulose ester is 100,000 or more.-   6. The transparent film for display substrate in any one of The    aforementioned 1 through 4, wherein the substituent of the cellulose    ester satisfies the following formula (A) and (B):    0≦Y≦1.5   Formula (A)    1.0≦X+Y≦2.9   Formula (B)

(wherein “X” denotes the degree of substitution and “Y” indicates thedegree of substitution by using a substituent containing an alkoxysilylgroup).

-   7. The transparent film for display substrate in any one of The    aforementioned 1 through 6, wherein the degree of substitution of    said cellulose ester by the acetyl group is 2.2 through less than    2.9.-   8. The transparent film for display substrate in any one of The    aforementioned 1 through 7, wherein the transparent film contains a    crosslinked polymer and the cellulose ester and the crosslinked    polymer forms a semi-IPN (semi-interpenetrating polymer network)    type polymer alloy.-   9. The transparent film for display substrate of The aforementioned    8, wherein the transparent film contains the crosslinked polymer in    an amount of 5 through 50 percent by mass of the transparent film.-   10. The transparent film for display substrate in any one of The    aforementioned l through 9, wherein the transparent film is composed    of a cellulose film of which glass-transition temperature obtained    by thermal mechanical analysis (TMA) is 180 degrees Celsius or more,    and the coefficients of linear expansion in both MD and TD    directions are in the range from 5 through 50 ppm/degrees Celsius.-   11. The transparent film for display substrate in any one of The    aforementioned 1 through 10 wherein, when the in-plane retardation    value at the wavelength of 590 nm is R₀ (590) and the in-plane    retardation value at the wavelength of 480 nm is R₀ (480), the ratio    [R₀(480)/R₀(590)] is not less than 0.8 through less than 1.0.-   12. A display substrate wherein a moisture proof film containing a    metal oxide or metal nitride is formed on at least one of the    surfaces of a transparent film for display substrate in any one of    The aforementioned 1 through 11, and a transparent conductive film    is formed on the moisture proof film or on the surface opposite to    the surface where the moisture proof film is formed.-   13. The display substrate of The aforementioned 12, wherein said    moisture proof film is mainly composed of silicon oxide.-   14. The display substrate of The aforementioned 12 or 13, wherein    the moisture proof film and the transparent conductive film is    formed by applying a high frequency voltage between opposed    electrodes under atmospheric pressure or under approximately    atmospheric pressure for a discharge, generating a reactive gas in    the plasma state by the discharge, exposing the transparent film for    display substrate to the reactive gas in the plasma state whereby    the moisture proof film and the transparent conductive film are    formed on the transparent film.-   15. A liquid crystal display using the display substrate in any one    of The aforementioned 12 through 14.-   16. An organic electroluminescence display using the display    substrate in any one of The aforementioned 12 through 14.-   17. A touch panel using the display substrate in any one of the    aforementioned 12 through 14.-   18. A method for manufacturing a transparent film for display    substrate according to a casting film forming method, comprising the    steps of:

casting the dope containing a cellulose ester and a plasticizer in anamount of less than 1 percent, onto a casting support member to form aweb;

drawing the web 3 through 100 percent both in the conveyance directionand the width direction; and drying the web.

-   19. A method for manufacturing a display substrate comprising the    steps of:

applying a high frequency voltage between opposed electrodes underatmospheric pressure or under approximately atmospheric pressure for adischarge,

generating a reactive gas in the plasma state by the discharge,

exposing the transparent film for display substrate formed by the methodof the aforementioned 18 to the reactive gas in the plasma state wherebythe moisture proof film and the transparent conductive film are formedon the transparent film.

-   20. The method for manufacturing a display substrate of the    aforementioned 19, wherein the frequency of the high frequency    voltage is in the range from 100 kHz through 2.5 GHz, and the supply    power is in the range from 1 W/cm² through 50 W/cm².-   21. The method for manufacturing a display substrate of the    aforementioned 20, wherein the frequency of said high frequency    voltage is in the range from 100 kHz through 150 MHz.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing representing an example of the plasma dischargeapparatus under the atmospheric pressure of the present invention or thepressure close to it;

FIG. 2 is a sketch representing an example of the structure of theconductive base material of the metal of a roll electrode or the likeand the dielectric covering the same;

FIG. 3 is a sketch representing an example of the structure of the basematerial of the rectangular fixed electrode as an applicator wherein oneof the rectangular fixed electrode group has been picked up, and thestructure of the dielectric covering the same;

FIG. 4 is a perspective view representing a liquid crystal displaydevice;

FIG. 5 is a conceptual diagram representing an example of the structureof an organic electroluminescence display device; and

FIG. 6 is a cross sectional view showing an example of a touch panel.

BEST MODE FOR CARRYING OUT THE INVENTION

The following describes the details of the present invention:

The transparent film for display substrate in the present inventionrefers to the transparent plastic film used as a support member or asubstrate for such an electronic device as a liquid crystal display,organic electroluminescence display and touch panel.

These transparent films for display substrate are required to provide afirm support of various types of functional thin films constituting suchan electronic device as a liquid crystal display, organicelectroluminescence display and touch panel. Further, these films arealso required to have superb flexibility and light weight.

In the meantime, the display substrate is required to ensure that thedisplay device having been formed is isolated from the outside airincluding moisture and oxygen. When used as a substrate, low moistureand oxygen permeability must be ensured. Normally, when a plastic filmis used as a substrate, the film must be coated with a moisture proofthin film such as a silicon oxide film.

A conductive thin film is also essential as the common functional thinfilm constituting the aforementioned display device. For example, an ITOfilm is used as a transparent conductive film.

These thin films are basically made of metallic oxide. There is noproblem if they are formed on a substrate such as glass characterized bysmaller expansion and contraction due to heat or moisture. However, thesubstrate made of plastic is subjected to conspicuous expansion andcontraction due to heat and moisture. Thus, expansion and contraction ofthe substrate are caused by thermal hysteresis in the production process(rise of temperature due to processing of the substrate of various typesof materials by vapor deposition and sputtering). Thus, opticaldisplacement, for example, is caused between layers. Especially themetallic oxide film formed on the substrate is vulnerable to cracks dueto expansion and contraction resulting from exposure to heat andmoisture, because of brittleness. This film is prone to characteristicvariation.

Thus, the plastic film used as a support member or substrate of theaforementioned electronic device is less vulnerable to the expansion andcontraction due to drastic changes in temperature and humidity in theprocess of manufacturing the functional thin film constituting theelectronic device. The thin film having been formed is less subjected tofracture (such as cracks and separation). Further, the functional thinfilm having been formed, such as a moisture proof film or a transparentconductive film is required to be resistant to cracks, even when exposedto bending force.

It is also required that the expansion and contraction of the substratecaused by changes in temperature and humidity in the environment where adisplay apparatus is used (e.g. heat by the backlight of the liquidcrystal display apparatus) do not cause a change in the characteristicsof the moisture proof film and conductive film formed on the substrate.

The glass having been used as a substrate material has a low expansioncoefficient. When it is used as a substrate or as a protective sheet toseal devices, it has been used preferably.

The present inventors have found out a film preferably used to take theplace of glass as a substrate material. This film is furthercharacterized in that glass-transition temperature obtained by thermalmechanical analysis (TMA) is 180 degrees Celsius (° C.) or more, and thecoefficients of linear expansion in both the MD and TD directions are inthe range from 5 through 50 ppm/degrees Celsius.

The transparent film of the present invention for display substrate hasa characteristic like this and is characterized in that the film havingsuch performances contains a cellulose ester with plasticizer contentaccounting for less than 1 percent, and is drawn 3 through 100 percentboth in the conveyance direction and the width direction.

The transparent film for display substrate is preferred to be acellulose ester film formed by the casting method. In the manufacturingprocess of cellulose ester film, the cellulose ester film is drawnacross the width. In this case, the direction of mechanical conveyancewill hereinafter be called the MD direction, and the directionperpendicular thereto will be called the TD direction.

When the linear expansion coefficient of the transparent film fordisplay substrate is in the aforementioned range, the functional thinfilm formed on the film such as the aforementioned moisture proof filmor transparent conductive film does not lose the aforementionedcharacteristics even when exposed to thermal hysteresis at the time ofmanufacture or the stress caused by heat or bending of the substratesubsequent to formation of the device on the substrate.

The linear expansion coefficient of the transparent film for displaysubstrate in the present invention can be obtained from thetemperature-strain curve in the thermal mechanical analysis (TMA).

The TMA-SS6100 by Seiko Instrument Co., Ltd. is used as an actualmeasuring instrument. A sample having a film thickness of 100 μum and awidth of 4 mm is fixed at a chuck distance of 20 mm, and the temperatureis increased from the room temperature to 180 degrees Celsius. After theresidual strain has been removed, the temperature is again increasedfrom the room temperature to 180 degrees Celsius at a rate of 5 degreesCelsius/min., whereby the linear expansion coefficient is obtained fromthe expansion of the chuck distance. For example, when the temperatureof the film material has rose 1 degree Celsius, and the size gasexpanded 0.001 mm (1 μm) per meter, the thermal expansion coefficient ofthe support member is said to be 1 ppm.

The transparent film for display substrate of the present invention is afilm containing the cellulose ester, and can be used in theaforementioned various types of electronic devices when such afunctional thin film as a moisture proof film or transparent conductivefilm is formed on the film.

A triacetyl cellulose, or a fatty acid cellulose ester mixed with acetylgroup, propionyl group or butyryl group can be used as the celluloseester. The cellulose ester is preferably used when the total degree ofsubstitution of all the acyl groups (total of the degree ofsubstitution) is greater than 1.5.

The glucose unit forming the cellulose has three hydroxyl groups thatcan be combined. For example, the degree of substitution by the acetylgroup in the cellulose triacetate is 3.0 when all three hydroxyl groupsof the glucose unit are bonded with the acetyl group.

In practice, replacement of all the hydroxyl groups is difficult due tothe problems with synthesis by high molecular reaction. The celluloseester having been subjected to complete acyl substitution does noteasily dissolve in the solvent. It has a high viscosity of solution andthe productivity is low.

In practice, what is commonly called triacetyl cellulose (TAC) has adegree of substitution of acetyl ranging from 2.8 through 2.9. Thetriacetyl cellulose (TAC) used in the cellulose ester of the presentinvention also has a degree of substitution of acetyl within this range.

What is commonly called the diacetyl cellulose (DAC) also has a degreeof substitution of acetyl ranging from about 2.2 through 2.5. Thediacetyl cellulose (DAC) is used in the cellulose ester of the presentinvention also has a degree of substitution of acetyl within this range.Accordingly, in the cellulose ester of the present invention, thepreferred degree of substitution of acetyl is 2.2 through 2.9.

The degree of substitution of acetyl group can be measured according tothe ASTM-D817-96.

The aforementioned acyl group can be substituted into the second, thirdand six positions of the glucose unit. Alternatively, it can besubstituted into the sixth position at a higher rate, for example. Sucha substitution accompanied by a certain distribution is also acceptable.

The cellulose ester resin used in the present invention can be thecellulose ester meeting the following formulae (A) and (B), for thepurpose of further upgrading the means for improvement including theorganic/inorganic hybrid or crosslinking to be described later:0≦Y≦1.5   Formula (A)1.0≦X+Y≦2.9   Formula (B)

In the aforementioned formulae, “X” denotes the degree of substitutionby the acetyl group of the hydroxyl group of cellulose as a skeleton,and “Y” indicates the degree of substitution by the substituentcontaining alkoxysilyl group.

There are three hydroxyl groups in the glucose in the cellulose. Whenall of them have been replaced, X+Y=3.0.

The ester group constituting these cellulose esters is acetyl group sothat a cellulose ester characterized by high heat resistance and lowlinear expansion coefficient is provided. For the purpose of furtherupgrading the modification effect by the organic/inorganic hybrid to bedescribed later, replacement can be achieved using the substituentwherein the residual hydroxyl group contains an alkoxysilyl group. Anexample includes the one wherein some of the hydroxyl group of thecellulose replaced by the silane coupling agent reacting therewith. Thesilane coupling agent preferably used is exemplified by glycide andisocyanate-based agents, such as γ-glycidoxypropyltrimethoxysilane,γ-glycidoxypropylmethyldimethoxysilane, 3-triethoxysilylpropylsuccinateanhydride, and γ-isocyanatepropyltrimethoxysilane. Especially,isocyanate based agents are preferred. The especially preferred silanecoupling agent is exemplified by γ-isocyanatepropyltrimethoxysilane. Thealkoxysilyl group replaced by the cellulose ester by reaction with themis subjected to polycondensation with alkoxysilane expressed by theaforementioned general formula (1), whereby a cellulose-silica hybridpolymer film is formed by the organic/inorganic hybrid in an integratedform. However, if the degree of substitution Y by alkoxysilyl group istoo large, the network structure of the transparent film will be tooclose and the film will be brittle. To prevent this, Y is preferably 1.5or less.

In the cellulose ester, X+Y is preferably not less than 1.0 through notmore than 2.9, because this ensures higher resin solubility and allows adope of high concentration to be produced. This is more advantageous atthe time of production and drying.

The cellulose ester has a preferable wavelength dispersioncharacteristic of birefringence and contains hydroxyl groups. Thesehydroxyl groups can be replaced by the substituent having an alkoxysilylgroup, as described above. When such a cellulose ester is used as askeleton, it is possible to produce a highly heat resistant transparentfilm characterized by low cost and birefringence, and positivewavelength dispersion of birefringence.

The positive wavelength dispersion of birefringence can be explained asfollows: For example, a high polymer is dissolved in a solvent thatpermits dissolution, and is cast and dried on a glass plate so that thefilm thickness will be 100 μm in the drying step. Then a film isproduced. The in-plane retardation value R₀ (480) of the film made ofthis high polymer at a wavelength of 480 nm and the in-plane retardationvalue R₀ (590) of the film made of this high polymer at a wavelength of590 nm are measured. In this case, the ratio [R₀(489)/R₀(590)] issmaller than 1.

In the transparent support member used in the laminated film in thepresent invention, the value obtained by-dividing the in-planeretardation value R₀ (480) at a wavelength of 480 nm by the in-planeretardation value R₀ (590) at a wavelength of 590 nm, R₀/(480)/R₀(590)is preferably 0.8 or more through not more than 1.0.

In a transparent film characterized by positive wavelength dispersion ofbirefringence, compensation for polarization in the full-wavelength ofthe visible light is possible. In a liquid crystal panel using thedisplay method based on birefringence, color misregistration is notobserved, and excellent contrast is ensured in an organicelectroluminescence display device.

No restriction is imposed on the cellulose ester as the material of thecellulose used in the present invention. It is exemplified by cottonlinter, wood pulp and kenaf. The cellulose obtained therefrom can beused independently or can be mixed at desired proportions for use. Useof not less than 50 percent by mass cotton linter is preferred.

The molecular weight of the cellulose ester usable in the presentinvention is preferably 70,000 through 200,000 in terms of numberaverage molecular weight (Mn), and more preferably 100,000 through200,000, from the viewpoint of the modulus of elasticity of the film tobe produced, dope viscosity and film formation speed. The cellulosederivative used in the present invention has an Mw/Mn ratio of less than3.0, and preferably 1.4 through 2.3.

The average molecular weight and molecular weight distribution of thecellulose ester can be measured using a high-speed liquidchromatography. The number average molecular weight (Mn) and weightaverage molecular weight (Mw) can be calculated using thesemeasurements, and the ratio thereof can be calculated.

The following describes the measurement conditions:

Solvent: Methylene chloride

Column: Shodex K806, K805, K803G (three columns by Showa Denko K.K. wereconnected for use)

Column temperature: 25 degrees Celsius

Sample concentration: 0.1 percent by mass

Detector: RI Model 504 (by GL Science Inc.)

Pump: L6000 (by Hitachi Limited)

Flowrate: 1.0 mL/min.

Calibration curve: Standard polystyrene STK (by Toso Co., Ltd.)

A calibration curve was used, where thirteenth samples of MW rangingfrom 1,000,000 through 500 were employed. Thirteenth samples arepreferably arranged at an equally spaced interval.

The cellulose ester used in the present invention can be synthesizedusing acid anhydride and acid,chloride as an acylating agent. When acidchloride is used as the acylating agent, organic acid (e.g. acetic acid)and methylene chloride are used as a reaction solvent. An acid catalystsuch as sulfuric acid is used as a catalyst. When acid chloride is usedas an acylating agent, a basic compound is used as a catalyst. Accordingto the commonest method of synthesis in the industry, cellulose isesterified by the mixed organic acid components containing the organicacid corresponding to the acetyl group (e.g. acetic acid and propionicacid anhydride) or the acid anhydride (e.g. acetic acid anhydride andpropionic acid anhydride), whereby cellulose ester is synthesized. Whenother acylating agent is used in combination, adjustment is made, forexample, to ensure that the amount of propionylating agent used will bewithin the range of the degree of substitution required by the ester tobe synthesized. The amount of the reaction solvent to be used ispreferably 100 through 1,000 parts by mass, more preferably 200 through600 parts by mass with respect to 100 parts by mass of cellulose. Theamount of the acid catalyst to be used is 0.1 through 20 parts by mass,more preferably 0.4 through 10 parts by mass, with respect to 100 partsby mass of cellulose.

The reaction temperature is preferably 10 through 120 degrees Celsius,more preferably. 20 through 80 degrees Celsius. Upon completion of acylsubstitution, hydrolysis (saponification) can be carried out wasrequired, so as to adjust the degree of substitution. Upon completion ofreaction, the reaction mixture is separated by the commonly practicedmethod, such as by sedimentation. Then cleaning and drying are performedto get a cellulose ester.

Dope is the solvent obtained by dissolving the cellulose ester, forexample, in the organic solvent such as methylene chloride, methylacetate, methanol and ethanol at a concentration of 10 through 35percent by mass (more preferably 15 through 25 percent by mass). Anadditive is added to the dope solution obtained by dissolving thecellulose ester, if required. This solution is cast onto the supportmember (produced by mirror-finishing of a belt- or drum-like stainlesssteel) (in a step of casting), and is heated. After part of the solventhas been removed (in the step of drying on the support member), the filmis separated from the support member, and the separated from is dried(in a step of film drying), whereby a cellulose ester is obtained. Afterdrying, the film is drawn in the MD and TD directions if required, aswill be described later in details. It is concurrently or sequentiallydrawn in the MD and TD directions until it is drawn 3 through 100percent. This procedure causes molecular orientation so that the linearexpansion coefficient of the film is reduced.

The transparent substrate film of the present invention for a displaycontains cellulose ester 50 to 100% by weight, more preferably 75 to 956by weight. In addition to the cellulose ester, the transparent substratefilm of the present invention for a display contains constituents, suchas below-mentioned inorganic polymer, a crosslinking agent andcrosslinked polymer 0 to 50% by weight, more preferably 5 to 25% byweight.

To reduce the moisture permeability and to improve the film formationperformance, 1 through 20 percent by mass of plasticizer is added to thenormal cellulose ester film for photographs or the cellulose ester filmfor polarizer protection. The amount of the plasticizer contained in thetransparent substrate film for display in the present invention ispreferably less than 1 percent, for the purpose of reducing the linearexpansion coefficient.

In the present invention, the plasticizer is defined as a low molecularcompound having a molecular weight of less than 1,000, the compoundbeing chemically inactive (without chemical reaction of bonding with acellulose ester or polymerization).

In the prior art, 5 through 20 percent by mass was included in thecellulose ester as a support member of the negative film of thephotograph, or in the cellulose ester film for polarizer protection ofthe liquid crystal display.

This was intended to make up for the disadvantage of the celluloseester. Since the cellulose ester is highly hydrophilic, the moisturepermeability and expansion coefficient due to moisture are excessivelyincreased when the cellulose ester is formed into a film. To be morespecific, the plasticizer has the effect of reducing the moisturepermeability of the cellulose ester film and the moisture expansioncoefficient.

However, the present inventors have made it clear that addition of theplasticizer causes a change in physical properties such as a drasticreduction in the glass-transition temperature and a drastic rise ofthermal expansion coefficient.

As described above, a high resistance to heat and a low thermalexpansion coefficient are essential to the film or display substrate.Accordingly, in the present invention, the amount of the plasticizer iskept below 1 percent. If the amount to be added is less than 1 percent,the aforementioned adverse effect on cellulose ester is minimized. Thisamount is more preferably 0.3 percent or less. It is most preferred thatno plasticizer is added.

If the amount of the plasticizer to be added is as small as 1 percent orless, this will cause such an adverse effect as an increase in moisturepermeability and moisture expansion coefficient. However, absorption andpermeation of vapor can be controlled by forming a gas barrier in thecellulose ester film, as will be described later. This solves theproblem when it is used as a substrate film for display. Further,formation of a gas barrier layer is essential, independently of the typeof the plastic used for the substrate. It cannot be stated that the gasbarrier layer is essential only because the cellulose ester is used forsubstrate film. Further, similarly to thermal expansion coefficientmoisture expansion coefficient can be reduced by drawing operation, aswill be described later.

The plasticizer that can be used in the present invention includes apolyvalent alcohol ester based plasticizer, glycolate plasticizer,phosphoric acid ester plasticizer and phthalic acid ester plasticizer.

To put it more specifically, it is possible to usebutylphthalylbutylglycolate, ethylphthalylethylglycolate,methylphthalylethylglycolate, triphenylphosphate, tricresyl phosphate,cresyldiphenylphosphate, octyldiphenylphosphate,diphenylbiphenylphosphate, trioctylphosphate, tributylphosphate,diethylphthalate, dimethoxyethylphthalate, dimethylphthalate,dioctylphthlate, dibutylphthalate, di-2-ethylhexylphthalate,dicyclohexylphthalate, ehylphthalylethylglycolate,trimethylolpropanetribenzoate, pentaerithritoltetrabenzoate,dipentaerithritolpentabenzoate, etc. Two or more of these plasticizerscan be mixed for use.

A low molecular compound having a specific function can be added to thecellulose ester film of the present invention, as required. Such afunctional low molecular compound is exemplified by an ultravioletabsorber and retardation regulating agent used to ensure that the deviceinside the display substrate will not be deteriorated by ultravioletrays; a dye used to adjust the color tone of the display substrate; andan oxidant inhibitor used to avoid oxidation of these functionalmaterials.

These low molecular compounds are required to be not more than 1 percentby mass in terms of the sum total in the cellulose ester film.

In order to prevent the liquid crystal of a liquid crystal displayapparatus from being deteriorated in an outdoor environment beingexposed to the solar rays or the like, the ultraviolet absorber isrequired to have an excellent capacity of absorbing the ultraviolet rayshaving a wavelength of 370 nm or less, and to exhibit excellent liquidcrystal display performances. For this purpose, the ultraviolet absorberthat does not absorb the visible light having a wavelength of 400 nm ormore is preferred used. In the present invention, light transmittance ata wavelength of 370 nm is preferably 10 percent or less, more preferably5 percent or less, still more preferably 2 percent or less.

In the present invention, an ultraviolet absorber having two or morearomatic rings in a molecule is especially preferred.

There is no particular restriction imposed on the ultraviolet absorberused in the present invention. Such an ultraviolet absorber includesoxybenzophenone based compound, benzotriazole compound, salicylic acidester compound, benzophenone compound, cyanoacrylate compound, triazinecompound, nickel complex salt and inorganic powder. The preferably usedultraviolet absorber includes the benzotriazole ultraviolet absorber andbenzophenone ultraviolet absorber that are highly transparent and highlyresistant to deterioration due to liquid crystal device. Especiallypreferred is the benzotriazole ultraviolet absorber where unwantedcoloring is minimized. Specific examples of the ultraviolet absorberpreferably used in the present invention are5-chloro-2-(3,5-di-sec-butyl-2-hydroxylphenyl)-2H-benzotriazole,(2-2H-benzotriazole-2-yl-6-(dodesyl of straight and sidechains)-4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone,2,4-benzyloxybenzophenone, and Tinuvin such as Tinuvin 109, Tinuvin 171,Tinuvin 234, Tinuvin 326, Tinuvin 327 and Tinuvin 328 which are theproducts of Chiba Special Chemicals Inc. and are available on themarket.

The ultraviolet absorber can be a mixture of two or more substances. Ahigh molecular ultraviolet absorber is also used preferably as theultraviolet absorber. Especially the polymer type ultraviolet absorberdisclosed in the Official Gazette of Japanese Patent Tokkaihei 6-148430is preferably used.

The method of adding the ultraviolet absorber is described below: Oneway is to dissolve the ultraviolet absorber in such an organic solventas alcohol, methylene chloride and dioxolane. Then dope is added.Another way is to add it directly in the dope composition. In the caseof the inorganic powder or the like that does not melt in the organicsolvent, it is dispersed in the organic solvent and cellulose esterusing a dissolver and sand mill, and then the dope is added.

The amount of the ultraviolet absorber to be used varies depending onthe type of the compound and operating condition. If the thickness ofthe dried cellulose ester film is 30 through 200 μm, the excessiveamount of ultraviolet absorber may act as a plasticizer. To avoid this,the amount of the ultraviolet absorber should be such that the linearexpansion coefficient will not deteriorate; namely, the preferred amountis not more than 1 percent by mass, similarly to the case of theplasticizer.

Further, an oxidant inhibitor, anthraquinone based dyestuff for tinctureadjustment and others can be added.

It is also possible to add the matting agent of fine particle includingsilicon oxide, and the fine particles of the matting agent such as thesilicon oxide surface-treated by an organic substance. The mattingeffect will be greater when the average diameter of the fine particlesis greater, while the smaller average diameter leads to bettertransparency. Thus, the average particle diameter of the fine particlesis preferably 5 through 50 nm, and more preferably 7 through 20 nm.

There is no particular restriction to the fine particles of the siliconoxide. The examples are AEROSIL 200, 200V, 300, R972, R972V, R972CF,R974, R202, R805, R812, OX50 and TT600 by Nihon Aerosil Co., Ltd. Use ofAEROSIL 200, 200V, R972, R972V, R974, R202, R805 and R812 is preferred.

Additives can be added to dope in batches. It is also possible toprepare an additive solution separately and to add it in line. In-lineaddition of part or whole of the matting agent is preferred in order toreduce the load on the filter medium.

To ensure better mixing with the dope during the in-line addition of theadditive solution, a small amount of cellulose ester is preferablydissolved. The amount of cellulose ester is preferably 1 through 10parts by mass, or more preferably 3 through 5 parts by mass, withrespect to 100 parts by mass of solvent.

Such an in-line mixer as the Static Mixer (Toray Engineering Inc.) orSWJ (Hi-Mixer, a Toray Static type in-line mixer), for example, ispreferably used for in-line addition and mixing in the presentinvention.

The transparent film of the present invention for a display substratecontaining cellulose ester can be modified by a technique calledorganic/inorganic hybrid method. The organic/inorganic hybrid methodprovides a technique for creating a material having the properties ofboth the organic and inorganic substances, by mixing the organicsubstance with the inorganic substance.

In the present invention, the aforementioned cellulose ester ispreferably used as the organic substance, while the inorganic highpolymer obtained by hydrolysis and polycondensation of the alkoxysilaneexpressed in the aforementioned general formula (1) is preferablyemployed as the inorganic substance.R_(4-n)Si(OR′)_(n)   General formula (1)

When the inorganic high polymer obtained by hydrolysis andpolycondensation of the alkoxysilane expressed in the aforementionedgeneral formula (1) is expressed in the general formula (2), theinorganic high polymer is preferably contained in the amount of 1through 20 percent by mass, relative to the entire film.R_(4-n)SiO_(n/2)   General formula (2)

If the inorganic high polymer containing a large number of hydrophilicgroups is added, hydrogen bondage between the cellulose ester moleculesis tightened and the glass-transition temperature rises. However, if itis added in the amount over a predetermined level, the substrate filmfor display becomes brittle. To overcome this difficulty, the amount tobe added is preferably not more than 20 percent by mass, more preferablynot more than 3 through 15 percent by mass or still more preferably notmore than 5 through 10 percent by mass.

If the amount to be added is within the aforementioned range, thetransparent film for display substrate using the cellulose ester filmmodified by the organic/inorganic hybrid is provided with furtherpreferable properties.

In the aforementioned general formula (1), R′ denotes a hydrogen atom ora monovalent substituent, and “n” indicates 3 or 4.

The alkyl group represented by R′ includes the methyl group, ethylgroup, propyl group, butyl group, and methoxyethyl group. It can bereplaced by the substituent (e.g. halogen atom, alkoxy group). Thealkoxy group is desorbed by hydrolysis and polycondensation of thealkoxysilane to produce alcohol. A lower alkoxy group that volatilizeseasily when dried is preferred. Especially methyl and ethyl groups arepreferably used.

The monovalent substituent represented by R can be any compound thatexhibits the properties of alkoxysilane. To put it more specifically, itincludes alkyl group, cycloalkyl group, alkenyl group, aryl group,aromatic heterocyclic ring group, and silyl group. Among them, preferredexamples are the alkyl group, cycloalkyl group and alkenyl group. Theycan be further replaced. The substituent of R includes a halogen atomsuch as fluorine atom and chlorine atom, amino group, epoxy group,mercapto group, hydroxyl group and acetoxy group. In particular, varioussubstituents that do not lose the properties of alkoxysilane can bementioned.

The specific examples of the preferably used alkoxysilane expressed inthe general formula (1) are: tetramethoxysilane, tetraethoxysilane(TEOS), tetra n-propoxysilane, tetraisopropoxysilane, tetran-butoxysilane, tetra t-butoxysilane, tetrakis(methoxyethoxy)silane andtetrakis(methoxypropoxy)silane. The examples further include:methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane,ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane,n-butyltrimethoxysilane, i-butyltrimethoxysilane,n-hexyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane,3-aminopropyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,3-chloropropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane,acetoxytriethoxysilane,(heptadecafluoro-1,1,2,2-tetrahydrodesyl)trymethoxysilane,(3,3,3-trifluoropropyl)trimethoxysilane,(3,3,3-trifluoropropyl)trimethoxysilane, andpentafluorophenylpropyltrimethoxysilane. The examples further include:vinyltrimethoxysilane, vinyltriethoxysilane, phenyltrimethoxysilane,vinyltrimethoxysilane, and vinyltriethoxysilane.

It is also possible to use the silicon compound of condensation productswith several molecules such as Silicate 40 and Silicate 45, Silicate 48and M Silicate 51 by Tama Chemical Co., Ltd., the silicon compound beingformed by partial condensation of these compounds.

The aforementioned alkoxysilane has a silicon alkoxide group subjectedto hydrolysis and polycondensation. Thus, a network structure of theinorganic high molecular compound is formed by hydrolysis andpolycondensation of these forms of alkoxysilane. The alkoxysilane or theproduct of hydrolysis and polycondensation is made to undergo finedispersion in the cellulose ester, thereby producing a transparent filmhaving both the properties of the organic high polymer composed ofcellulose ester and those of the inorganic high polymer formed byhydrolysis and polycondensation.

To put it more specifically, a hydrophilic organic solvent such asmethanol, ethanol and acetonitryl is made to coexist in order tofacilitate mixing of hydrophobic alkoxysilane and water, or the organicmetal compound and water, as required. A catalyst is added if required,so that hydrolysis and polycondensation of alkoxysilane are carried out.Then the product of hydrolysis and polycondensation is added to the dopeof the cellulose ester is mixed with it, thereby causing fine dispersionin the cellulose ester.

Further, the good solvent of the cellulose ester is preferably includedin order to prevent cellulose ester from being precipitated out of thedope when alkoxysilane or the product of hydrolysis and polycondensationthereof are added to the dope of the cellulose ester.

From the viewpoint of productivity in film haze, flatness, film makingspeed and solvent recycling, water content for hydrolysis andpolycondensation of alkoxysilane in the dope is preferably within therange of 0.01 or more without exceeding 2.0 percent by mass.

Use of a transparent film as a transparent support member improves theheat resistance without losing the optical characteristics of thecellulose ester, and provides a film impervious to deformation at a hightemperature.

The aforementioned cellulose ester is used as the cellulose ester use inthe transparent film whose major component is the cellulose ester andthe product of hydrolysis and polycondensation of alkoxysilane. Acetylcellulose is particularly preferred. As described above, the celluloseester (Y>0) modified by the alkoxysilyl group capable of condensationreaction with the product of hydrolysis and polycondensation ofalkoxysilane is also used preferably.

In the transparent film composed of the cellulose-silica hybrid polymerby the organic/inorganic hybrid of the present invention, a catalyst canbe added to the alkoxysilane expressed in the aforementioned generalformula (1) at the time of hydrolysis if required, so as to promotecondensation reaction.

The catalyst used here includes: such inorganic acids as hydrochloricacid, sulfuric acid, nitric acid, phosphoric acid,dodecatungstophosphoric acid (VI), dodecamolybdophosphoric acid (VI) andtungstosilicic acid; and such organic acids as acetic acid,trifluoroacetic acid, levulinic acid, citric acid, p-toluenesulfonicacid and methanesulfonic acid. A base can be added to promoteneutralization after sol-gel reaction processes subsequent to additionof acids. When the base is added to promote neutralization, the contentof alkali metal is preferably below 5,000 ppm prior to the step ofdrying (where the alkali metal also includes the ionized substance).Further, Lewis acid, for example, metallic acetate such as germanium,titanium, aluminum, antimony and tin; other organic acids, halogenatedcompound, and phosphoric acid can be used in combination.

Instead of the aforementioned acids, the following can be used as acatalyst: ammonium, monoethanolamine, diethanolamine, triethanolamine,diethylamine and triethylamine; bicyclo ring based amine such as DBU(diazabicycloundecene-1) and DBN (diazabicyclononene); and a base suchas ammonium, phosphine, alkali metal alkoxide, ammonium hydroxide,tetramethylammonium hydroxide and benzyltrimethylammonium hydroxide.

There is no particular restriction to the amount of the acid or alkalicatalyst to be added. It is preferably 0.01 through 20 percent by massrelative to the amount of water to be added. Further, processing of acidand base can be used in combination several times. The catalyst can beneutralized, or the volatile catalyst can be removed by pressurereduction or by separation of liquid and washing by water. It is alsopossible to use such a solid catalyst as an ion exchange resin, which isconvenient for removal of the catalyst.

The reaction of hydrolysis and polycondensation of alkoxysilane may becompleted in the molten state prior to coating, or in a film-like formafter casting. It is preferably completed prior to coating. Depending onthe type of application, reaction need not be completed thoroughly, butit is preferably completed thoroughly wherever possible.

The cellulose ester film of the present invention can be modified by acrosslinking agent. Modification can be achieved by crosslinking by thecompound whose molecule contains a plurality of reactive groups thatbond with the residual hydroxy group by reaction. 1 through 20 percentby mass of such a crosslinking agent is preferably contained withrespect to the entire cellulose ester film. This includes thecrosslinking formed in the cellulose ester by reaction of theaforementioned reactive group with the residual hydroxyl agent of thecellulose ester.

If more than 20 percent by mass of the crosslinking agent is added, thefilm will be brittle and the amount of addition will exceed theequivalent of the residual hydroxyl group of the cellulose ester.Coloring may be caused by reaction with moisture in the air. Thus,addition of such an excessive amount should be avoided. Further, if thedegree of crosslinking is low, heat resistance of the cellulose esterfilm cannot be improved. Not less than 1 percent by mass of thecrosslinking agent is preferably added. Addition of 5 through 15 percentby mass of the crosslinking agent is more preferred.

This arrangement further improves the linear expansion coefficient. Thereactive group that bonds with the residual hydroxyl group of celluloseester by reaction is preferably an addition reactive group. To put itmore specifically, it includes isocyanate group, thioisocyanate group,epoxy group and acid anhydride group. What is particularly preferred isa polyisocyanate compound containing a plurality of isocyanate groupscrosslinkable with the cellulose ester.

The aforementioned polyisocyanate includes the compound expressed in thefollowing general formula:O═C═N-L-(N═C═O)_(v)   General formula

In the formula, v denotes 0, 1 or 2. L indicates a divalent bondinggroup containing the alkylene group, alkenylene group, arylene group oraralkyl group as a partial structure.

These groups may contain a further substituent. Preferred examples ofthe substituents are halogen (e.g. Br and Cl), hydroxyl group, aminogroup, carboxyl group, alkyl group and alkoxysilyl group.

They are exemplified by the isocyanate having an aromatic ring, such as2,4-trilenediisocyanate (TDI), 4,4′-diphenylmethanediisocianate (MDI)and xylylenediisocyanate; the aliphatic isocyanate such asn-butyldiisocyanate and hexamethylenediisocyanate; and the isocyanatewith hydrogen added to the aromatic ring such as hydrogenated TDI andhydrogenated MDI. The examples also include Desmodur N100, DesmodurN3300, Mondur TD-80, Mondur M and Mondur MRS and polymer isocyanate byMobey Inc.: Papi 27 by Dow Inc.; Octadecilisocyanate by Aldrich Inc.;Coronate 2030, Coronate 2255, Coronate 2513, Coronate 2507, Coronate L,Coronate HL, Coronate HK, Coronate HX, Coronate 341, Coronate MX andCoronate 2067 by Nippon Polyurethane Co., Ltd.; Takenate D103H, TakenateD204EA, Takenate D-172N and Takenate D-170N by Takeda ChemicalIndustries, Ltd.; and Sumujule N3200, Sumujule 44V-20 and Sumujule IL bySumitomo Bayer Urethane Inc., without the present invention beingrestricted thereto.

The crosslinking agent other than the isocyanate compound includes:pyromellitic dianhydride, biphenyltetracarboxylic dianhydride,benzophenonetetracarboxylic dianhydride, diphenylsulfonetetracarboxylicdianhydride, ethylenediaminetetraacetic dianhydride,naphthalenetetracarboxylic dianhydride, cyclohexanetetracarboxylicdianhydride, and paraphenylenediisocyanate, without the presentinvention being restricted thereto.

Their amount of use is 1 through 20 percent, preferably 1 through 5percent in terms of mass ratio, relative to cellulose ester film. If theamount is excessive, excessive crosslinking will result, and the productwill be brittle. If the amount is insufficient, the advantages of thepresent invention cannot be provided.

The compound whose molecule contains a plurality of the reactive groupsbonding with hydroxyl group by reaction is preferably added directlyinto the dope to be dissolved therein, or is added in the form of liquiddissolved in an organic solution, in order to ensure uniform mixing withthe dope solution. It is also possible to prepare the solutions of thesecompounds separately, which are added into the dope solution immediatelybefore being cast onto the belt or drum.

Especially when the crosslinking reaction is carried out quickly, it isalso possible to perform sequential in-line addition immediately beforethe step of casting onto the belt or drum. This arrangement encouragescrosslinking reaction on the belt or drum support member in the castingstep, or in the web subsequent to separation.

The display substrate film containing the cellulose ester film of thepresent invention can be modified by the technique called the semi-IPN(semi-interpenetrating network structure) type polymer alloy method.

The IPN polymer alloy is composed of crosslinked polymers based oninterpenetrating polymer network. The semi-IPN polymer alloy is made upof the crosslinked polymer and non-crosslinked polymer.

The semi-IPN polymer alloy can be produced by crosslinked polymerizationof the monomer and/or oligomer for crosslinked polymer when thenon-crosslinked polymer is dissolved. Alternatively, the semi-IPNpolymer alloy can also be produced by non-crosslinked polymerization ofthe monomer when crosslinked polymer is swollen by the monomer and/oroligomer in the presence or absence of solvent. In the presentinvention, the crosslinked polymer and the non-crosslinked polymer arenot required to be completely compatible. They can be phase-separated.Even when the crosslinked polymer and the non-crosslinked polymer arephase-separated, the crosslinked polymer rich phase and non-crosslinkedpolymer rich phase are formed in a semi-IPN structure. However, in thepresent invention, the crosslinked polymer and non-crosslinked polymerproduced in a particulate form are not blended together. This can beverified by checking that much of the crosslinked polymer is notdispersed in a particulate form when the film of the present inventionis dipped in the solvent for dissolving the non-crosslinked polymer.

The film composed of the semi-IPN polymer alloy has both the physicalproperties of excellent hardness and heat resistance as the propertiesof the crosslinked polymer, and the physical properties of flexibilityand optical characteristics as the properties of the non-crosslinkedpolymer.

The non-crosslinked polymer of the present invention is a celluloseester characterized by excellent transparency and low birefringence aswell as positive waveform dispersion characteristics in birefringence.

There is no particular restriction to the cross linked polymer used inthe semi-IPN polymer alloy. It is exemplified by epoxy resin, phenolresin, melamine resin, crosslinked vinyl polymer and polycyanulate. Thecross-linked vinyl polymer characterized by excellent transmittance andheat resistance is preferably used. The crosslinked vinyl polymer isobtained by polymerization of the low-molecular compound through heatingor applying an energy ray.

The low-molecular compound of the present invention refers to thecompound that has a molecular weight of 1,000 or less and cannot beformed into a film as a simple substance.

The low-molecular compound containing a polymerized unsaturated doublebond used in the present invention includes the low-molecular compoundexemplified by the alkenyl group such as vinyl group and allyl group;and the unsaturated fatty acid residue such as acryl acid residue andmethacryl acid residue.

There is no particular restriction to the polymerized unsaturated doublebond used in the present invention. It preferably contains thefunctional group capable of interaction through hydrogen bond withcellulose ester in such a way that compatibility will be ensured,without generation of haze, bleeding out or volatilization, in themixing phase prior to polymerization.

The aforementioned functional group includes: hydroxyl group, ethergroup, carbonyl group, ester group, carboxylic acid residue, aminogroup, imino group, amido group, cyano group, nitro group, sulfonylgroup, sulfonic acid residue, phosphonyl group and phosphonic acidresidue. The carbonyl group, ester group and phospholyl group arepreferably used.

A low-molecular compound having an unsaturated fatty acid residue suchas acrylic acid, methacrylic acid, undecylenic acid, oleic acid, sorbicacid, linolic acid, linolenic acid, arachidonic acid, and others ispreferably used as the aforementioned functional group characterized byhaving a polymerized unsaturated double bond.

Further, the compound characterized by a high polymerization speed andcurable by energy ray is preferred. Accordingly, the preferred compoundis the low-molecular compound of the acryl and/or methacryl (alsodescribed as (meth)acryl: also applicable to (meth)acryl group,(meth)acrylate and (meth)acryloyl), namely, the compound containing the(meth)acryloyl group.

Esters between (meth)acrylic acid and polyvalent alcohol can bementioned as the low-molecular compound, meeting the aforementionedconditions, capable of giving heat resistance to the cross-linkedpolymer, and containing a plurality of polymerized unsaturated doublebonds preferably used in the present invention.

Esters between (meth)acrylic acid and polyvalent alcohol can bementioned as the low-molecular compound, meeting the aforementionedconditions, capable of giving heat resistance to the cross-linkedpolymer, and containing a plurality of polymerized unsaturated doublebonds preferably used in the present invention.

The polyvalent alcohol used in the present invention can be expressed inthe following general formula (4):R¹—(OH)_(n)   General formula (4)

In this formula, R¹ indicates an n-valent organic group, n shows apositive integer representing 2 or more, OH group denotes an alcoholicgroup and/or phenolic hydroxyl group.

The following describes the examples of the preferably used polyvalentalcohol, without the present invention being restricted thereto:

Examples are adonitol, arabitol, ethylene glycol, diethylene glycol,triethylene glycol, tetraethylene glycol, 1,2-propanediol,1,3-propanediol, dipropylene glycol, tripropylene glycol,1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol,1,2,4-butanetriol, 1,5-pentandiol, 1,6-hexanediol, hexanetriol,galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol, sorbitol,trimethylolpropane, trimethylolethane and xylitol. Especiallytriethylene glycol, tetraethylene glycol, dipropylene glycol,tripropylene glycol, sorbitol, trimethylolpropane, and xylitol arepreferable.

One type of the unsaturated carboxylic acid having a polymerizedunsaturated double bond may be used for the polyvalent alcohol ester.Alternatively, two or more of the unsaturated carboxylic acids may bemixed for use. All the OH groups in the polyvalent alcohol can beesterified or some of these OH groups can be kept unchanged.

The following shows the specific compounds of the polyvalent alcoholunsaturated carboxylic acid ester:

In addition to the above, the following compounds are also usedpreferably as the low-molecular compound having a plurality ofpolymerized unsaturated double bonds:

The examples are: divinylsulfone, divinylbenzene, 1,4-butandiolether,diallylamine, diallylsulfide, diallyldisulfide, diallylphthalate,triallyltriazine-2,4,6(1H, 3H, 5H)-trione,N,N′-1,3-phenylenedimaleimide, N,N′-1,4-phenylenedimaleimide,(3-acryloxypropyl)trimethoxysilane, allyltriethoxysilane,allyltriphenylsilane, (5-bicycloheptenyl)triethoxysilane,boronvinyldimethylsiloxide, butenyltriethoxysilane,divinyldimethylsilane, divinyltetramethyldisilane,1,3-diallyltetramethyldisiloxane, 1,3-divinyl-1,3-diphenyl-1,dimethyldisiloxane, hexavinyldisiloxane,methacryloxyethoxytrimethylsilane,methacryloxypropylheptacyclopentyl-T8-sylsesquioxane,octavinyl-T8-sylsesquioxane, methacryloxypropylmethyldiethoxysilane,methacryloxypropyltrimethoxysilane,methacryloxypropyltris(vinyldimethylsiloxy)silane,pentavinylpentamethylcyclopentasiloxyne, styrylethyltrimethoxysilane,tetraallylsilane, tetraallyloxysilane,tetrakis(2-methacryloxyethoxy)silane,tetrakis(vinyldimethylsiloxy)silane,1,1,3,3-tetravinyldimethyldisiloxane, tetravinylsilane,1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane,trivinylethoxysilane, vinylmethyldimethoxysilane,1-phenyl-1-trimethylsiloxyethylene,2-trimethylsiloxy-4-allyloxydiphenylketone,tris(vinyldimethylsiloxy)methylsilane, trivinylethoxysilane,trivinylmethylsilane, trivinylsilane,1,3,5-trivinyl-1,3,5-trimethylcyclotrisilazane,1,3,5-trivinyl-1,1,3,3,5,5-pentamethyltrisiloxane,vinyltriacetoxysilane, vinyltriisopropenoxysilane,vinyltrimethoxysilane, aluminum acrylate, methacryloxytri-n-butyl tin,tetraallyl tin, boron vinyldimethylsiloxide, titanium allylacetoacetatetriisopropoxide, titanium methacrylateisopropoxide, zirconiumdimethacrylate dibutoxide, zirconium methacryloxyethylacetoacetatetri-n-propoxide, cupric methacryloxyethylacetoacetate, (metha)acrylicacid ester of epoxy resin, (metha)acrylic acid ester of polyester resin,(metha)acrylic acid ester of polyether resin, (metha)acrylic acid esterof polybutadiene resin, oligomer such as polyurethane resin having a(metha)acryloyl group on the molecular terminus.

The low-molecular compounds containing a polymerized unsaturated doublebond can be used singly, or two or more of them can be mixed for use.The low-molecular compound containing one polymerized unsaturated doublebond may be contained in the cross-linked polymer. To maintain the heatresistance of the cross-linked polymer, it is preferred that more than50 percent by mass of the cross-linked polymer be composed of aplurality of low-molecular compounds containing a polymerizedunsaturated double bond of the present invention.

The content of the cross-linked polymer of the present invention in thetransparent film is preferably 5 through 50 percent by mass relative tothe overall mass of the transparent film. If the amount of thecross-linked polymer is smaller than 5 percent by mass, the advantage ofimproving the heat resistance resulting from addition of thecross-linked polymer will not be provided, and the polymer tends to flowat the time of heating at a high temperature. This should be avoided. Ifthe amount of the cross-linked polymer exceeds 50 percent by mass, sincethe transparent film will be brittle, it may be preferably 50% by massor less.

In the semi-IPN polymer alloy film of-the present invention,low-molecular compounds containing a polymerized unsaturated double bondof the present invention in the cellulose ester of the present inventioncan be cross-linked by any desired method. It is preferably cross-linkedby application of an energy ray because of high polymerization speed andthe need of heating for dissolution of cellulose derivative in theorganic solvent.

The electron ray, gamma-ray, X-ray, ultraviolet ray, visible ray andinfrared ray can be used as an energy ray. Especially the ultravioletray is preferably used due to the simple structure of the equipment andease of handling. The intensity of the ultraviolet rays to be applied ispreferably in the range from 0.1 through 5,000 mW/cm², more preferablyin the range from 10 through 1,000 mW/cm². It can be applied for anyspan of time, but it is preferably applied for 0.1 through 100 secondsin many cases. When ultraviolet rays and visible rays are used as energyrays, a photo-polymerization initiator is preferably contained in orderto increase the polymerization speed. Further, if the ultraviolet raysare applied in the atmosphere of inert gas, polymerization speed can beincreased and the degree of polymerization can be improved.

A preferable photo-polymerization initiator is exemplified by a benzoylderivative, a benzylketal derivative such as Ingacure 651, anα-hydroxyacetophenone derivative such as 1-hydroxycyclohexylphenylketone(Ingacure 184), and an α-aminoacetophenone derivative such as Ingacure907.

An electron beam is another energy ray that is preferably used in thepresent invention. The electron beam is not affected by the ultravioletabsorbing effect of the solvent, coagulant solution and other additives.Use of the electron beam expands the scope of selecting these agents andimproves the film making speed. It should be added that, when heating isused for cross-linked polymerization, polymerization initiatorazobisisobutyronitril (AIBN) and benzoyl peroxide (BPO) is preferablyadded at a temperature higher than that in the casting step (−80 degreesCelsius) and lower than that in the drying step (−150 degrees Celsius).

In the semi-IPN polymer alloy, the precursor of the cross-linked polymerworks as a plasticizer prior to starting the cross-linkedpolymerization. This facilitates drawing operation and permits drawingto be performed at a higher magnification than in the case of a commoncellulose ester film. Conversely, after reaction of cross-linking,drawing cannot be performed. Thus, drawing operation is preferredcarried out prior to crosslinking.

The following describes the method of manufacturing a cellulose esterfilm, an organic/inorganic hybrid film containing the cellulose ester ora semi-IPN polymer alloy.

The transparent film for display of the present invention is preferredformed on a mirror-finished support member by dissolving a celluloseester and other additive independently or in a mixed organic solvent andby casting the dope obtained therefrom.

Before the step of casting, the cellulose ester is dissolved in theorganic solvent. It can be dissolved under the normal pressure or addedpressure. It can be dissolved by cooling (at 0 through 78 degreesCelsius) or by heating (at 40 through 150 degrees Celsius).

The film obtained by such casting production method is characterized bya high degree of flatness and is preferably used as a transparent filmfor display. An organic solvent ensuring effective dissolution ofcellulose ester is called a good solvent. The organic solvent, having amajor effect on the dissolution, used in great quantities is called amain (organic) solvent or major (organic) solvent.

Good solvents are exemplified by: ketone such as acetone, methylethylketone, cyclopentanone and cyclohexane; ethers such as terahydrofuran(THF), 1,4-dioxane, 1,3-dioxolane and 1,2-dimethoxyethane; esters suchas methyl formate, ethyl formate, methyl acetate, ethyl acetate,amylacetate and γ-butyrolactone; methyl cellosolve, dimethylimidazolinone, dimethyl formamide, dimethyl acetoamide, acetonitryl,dimethyl sulfoxide, sulfolane, nitroethane, methylene chloride, anddichloro ethane. Of these, 1,3-dioxolane, acetone, methyl acetate, andmethylene chloride are preferred.

The dope preferably contains 1 through 40 percent by mass of the alcoholhaving a number of carbon atoms of 1 through 4, in addition to theaforementioned organic solvents. After the dope has been cast onto themetallic support member, the solvent starts to evaporate and theproportion of alcohol increases, thereby gelating the web (indicatingthe dope film after the dope of the cellulose derivatives has been castonto the support member) so that a stronger web is created, and the webcan be removed easily from the metallic support member. To achieve this,the aforementioned substance is used as a gelatinizer solvent. It isalso used to promote the cellulose derivatives of the non-chlorine basedorganic solvent when this proportion is smaller, and to control thegelation, precipitation and increase of viscosity.

The alcohol with a number of carbon atoms of 1 through 4 is exemplifiedby: methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol,tert-butanol, and propylene glycol monomethyl ether. Of thesesubstances, ethanol is preferably used because it is characterized byexcellent dope stability, lower boiling point, quick drying and lack oftoxicity. These organic solvents independently do not dissolve cellulosederivatives, and are called poor solvents.

The most preferable solvent for dissolving the cellulose esterderivative as a preferred high molecular compound meeting theaforementioned requirements, to a high degree of concentration is themixture solution wherein the ratio between methylene chloride and ethylalcohol is 95:5 through 80:20.

The aforementioned additives can be added to dope in batches. It is alsopossible to prepare an additive solution separately and to add it inline. In-line addition of part or whole of the matting agent ispreferred in order to reduce the load on the filter medium.

To ensure better mixing with the dope during the in-line addition of theadditive solution, a small amount of cellulose ester is preferablydissolved. The amount of cellulose ester is preferably 1 through 10parts by mass, or more preferably 3 through 5 parts by mass, withrespect to 100 parts by mass of solvent.

Such an in-line mixer as the Static Mixer (Toray Engineering Inc.) orSWJ (Hi-Mixer, a Toray Static type in-line mixer), for example, ispreferably used for in-line addition and mixing in the presentinvention.

In the aforementioned casting step, the dope is fed to the pressure die,and the dope is cast from the pressure die onto the casting supportmember (hereinafter referred to as “support member” in some cases) of anendless metallic belt for endless feed or a rotating metallic drum.Another casting method is a doctor blade method wherein the thickness ofthe cast dope film is adjusted by a blade. However, use of a pressuredie such as a T-die or a coat hanger die is preferred because the formof the slit at the base portion can be adjusted and uniform filmthickness can be obtained easily.

There are three methods to heat the web on the casting support memberand to evaporate the solvent: The first method is to blow air from theweb side; the second is to use a liquid to transfer heat from the backof the support member; and the third is to use the radiant heat totransfer heat. The second method of using a liquid to transfer heat fromthe back of the support member is preferably used. A combination ofthese methods is also used preferably.

The web from which solvent has been evaporated on the support member isseparated at the position for separation. After that, the separated webis fed to the next process. If there is an excessive amount of thesolvent remaining on the web at the time of separation, separation willbe difficult. If the web is separated after having been driedsufficiently on the support member, part of the web will be separated inthe middle of the operation.

To increase the film making speed, it is possible to use a gel castingmethod capable of separation despite the presence of excessive amount ofresidual solvent. Gelation is performed by after dope casting adding apoor solvent for cellulose ester into the dope. Alternatively, gelationis performed by reducing the temperature of the support member. Ifseparation is carried out with a great deal of solvent still remaining,the flatness tends to be lost during separation, or a stretch or alongitudinal streak due to separation tension tends to appear if the webis soft. The amount of the residual solvent is determined according tothe tradeoff between economical speed and quality.

In the drying process, the web is dried by a drier wherein the web isalternately passed through the rolls arranged in a staggered form and isfed, or a tenter apparatus wherein the web is fed with both ends of theweb clipped by a clip. To dry the web, hot air is commonly blown to bothfaces of the web. Instead of air, microwave is also applied to the web.If the drying process is carried out too fast, the flatness of the filmtends to be damaged. Drying at a high temperature is preferably startedwhen the amount of residual solvent is 8 or less percent by mass.Generally, the drying temperature is 40 through 25 degrees Celsius,preferably 70 through 180 degrees Celsius, throughout the overallprocess. Drying conditions should be selected depending on the type andcombination of the solvent to be used.

In the step of drying after the web has been separated from the castingsupport member, the web tends to shrink across the width by evaporationof solvent. As drying is carried out faster at a high temperature,shrinkage will be greater. To minimize this shrinkage during the processof drying is important in ensuring the superb flatness of the film to beproduced. For this purpose, the method (tenter method) is preferred,wherein drying is carried out with both ends of the web held by a clipacross the width throughout the drying process or in some portion of thedrying process, as disclosed in the Official Gazette of Japanese PatentTokkaisho 62-46625.

The method disclosed in the Official Gazette of Japanese Patent Tokkai2003-55477 is preferably used in order to get a low linear expansioncoefficient of a cellulose acetate film after having been dried, the lowlinear expansion coefficient being preferable for a transparent film fordisplay substrate.

In the process of drawing, drawing is preferably performed in at leastone direction. To get a low linear expansion coefficient in all thedirections of the inner surface, biaxial orientation is more preferred.Biaxial orientation method is available in two types; simultaneousbiaxial orientation and sequentialbiaxial orientation. From theviewpoint of ensuring continuous production, the sequential biaxialorientation is preferred. After the dope is cast to produce a film, thefilm is separated from a band or drum and is then drawn. If the amountof the residual solvent expressed in the following formula at the timeof separation is excessive, the web will be difficult to separate.Conversely, if it is separated after having been dried sufficiently onthe support member, part of the web may be separated in the middle. Toavoid this problem, separation is preferably performed when the amountof the residual solvent is 10 through 120 percent by mass.

The temperature at the position of separation on the support member ispreferably 10 through 40 degrees Celsius, more preferably 11 through 30degrees Celsius. To facilitate separation, the amount of the residualsolvent at the position of separation is preferably 20 through 100percent by mass, more preferably 30 through 90 percent by mass.

Amount of the residual solvent={(M−N)/N}×100

where M denotes the mass of the web (film containing solvent).at adesired time point, and N indicates the mass when the web M has beendried for 3 hours at a temperature of 120 degrees Celsius.

Drawing is preferably performed at least once in each of thelongitudinal direction (MD) and transverse direction (TD). It ispreferred that drawing be performed in the longitudinal direction afterdrawing in the transverse direction.

(1) Drawing in the TD Direction

Before drawing of the preheated film in the TD direction, the film isheated preferably at 50 or more without exceeding 150 degrees Celsius,more preferably at 60 or more without exceeding 140, still morepreferably at 70 or more without exceeding 130. The film is preheatedpreferably for 5 seconds or more without exceeding 3 minutes, morepreferably for 10 seconds or more without exceeding 2 minutes, stillmore preferably for 15 seconds or more without exceeding 90 seconds.Preheating is preferably carried out with the film held by a chuck inthe tenter.

Drawing and preheating are followed by the step of drawing in the TDdirection. The drawing speed is preferably 5 through 300 percent/minute,more preferably 15 through 150 percent. In the present invention,drawing at such a low speed is preferable. (The normal polymer film(e.g. polyester) is commonly drawn at a speed higher than 500percent/minute). This drawing operation is performed preferably at 80 ormore without exceeding 160 degrees Celsius, more preferably at 90 ormore without exceeding 150 degrees Celsius, still more preferably at 100or more without exceeding 145 degrees Celsius. Drawing is preferablycarried out with both ends of the film held by a tenter. The stretchmagnification is preferably 3 percent or more without exceeding 100percent, more preferably 5 percent or more without exceeding 40 percent,still more preferably 7 percent or more without exceeding 35 percent,most preferably 10 percent or more without exceeding 30 percent. In thepresent invention, the film is preferably subjected to the followingprocessing:

a) The film is drawn in the longitudinal direction of preferably byraising the film temperature in the range 10 or more without exceeding30 degrees Celsius. The temperature to be raised is preferably 12 ormore without exceeding 28 degrees Celsius, more preferably 15 or morewithout exceeding 25. As a higher degree of orientation is achieved bydrawing, a smaller linear expansion coefficient is formed in thedirection of drawing. A film of brittle polymer such as a celluloseacetate film tends to break during the step of drawing. In thetransverse drawing, the film is gripped by a clip, and stress isconcentrated on the gripped portion and the film tends to break. Toensure a high degree of orientation without allowing the film to break,the drawing is preferably performed by raising the temperature. Further,in the present invention, when there is a great deal of residual solventand the film is plasticized, the film is drawn at a lower temperature.When the film temperature has risen and the solvent has evaporated, thefilm is drawing at a higher temperature. This arrangement ensuresbalanced drawing over the overall area on the inner surface of the filmwithout allowing the film to break, with the result that a film havingan improved linear expansion coefficient will be provided.

b) To avoid uneven linear expansion coefficient, after transversedrawing, the film tension is reduced and the film is shrunk preferablyin the range from 1 percent or more without exceeding 20 percent,preferably in the range from 2 percent or more without exceeding 15percent, preferably in the range from 4 percent or more withoutexceeding 12 percent, preferably at the drawing temperature of −50degrees Celsius or more without exceeding the drawing temperature, morepreferably at the drawing temperature of −40 degrees Celsius or morewithout exceeding the drawing temperature, still more preferably at thedrawing temperature of −30 degrees Celsius or more without exceeding thetemperature. This procedure will reduce the uneven drawing (bowing)having occurred in the transverse direction during drawing. Thisprocedure requires preferably 5 seconds or more without exceeding 300seconds, more preferably 10 seconds or more without exceeding 200seconds, still more preferably 15 seconds or more without exceeding 100seconds.

(2) Drawing in the MD Direction

Before the preheated film is drawn in the longitudinal direction, it ispreheated preferably at 50 or more without exceeding 150 degreesCelsius, more preferably at 60 or more without exceeding 140 degreesCelsius, still more preferably at 70 or more without exceeding 130degrees Celsius. The film is heated preferably for 5 seconds or morewithout exceeding 3 minutes, more preferably for 10 seconds or morewithout exceeding 2 minutes, still more preferably for 15 seconds ormore without exceeding 90 seconds. Preheating is preferably carried outby feeding the film on the roll and/or in the heating tank.

The drawing speed of the film to be drawn is preferably 50percent/minutes or more without exceeding 100 percent/minute, morepreferably 80 percent/minutes or more without exceeding 800percent/minute, still more preferably 100 percent/minutes or morewithout exceeding 700 percent/minute. The drawing temperature ispreferably 115 or more without exceeding 160 degrees Celsius, morepreferably 120 or more without exceeding 155 degrees Celsius, still morepreferably 125 or more without exceeding 150 degrees Celsius. Thestretch magnification is preferably 3 percent or more without exceeding100 percent, more preferably 5 percent or more without exceeding 40percent, still preferably 7 percent or more without exceeding 35percent, most preferably 10 percent or more without exceeding 30percent.

Dawning is preferably carried out by using a heat roll and/or radiantheat source (e.g. IR heater) or by using at least two nip rolls havingdifferent peripheral speeds (the peripheral speed at the outlet ishigher than that at the inlet) while the film is heated in athermostatic bath.

In the present invention, the film is preferably subjected to thefollowing processing:

a) To avoid uneven linear expansion coefficient, the temperature for theroll (nip roll on the inlet side) immediately before drawing operationis preferably 70 or more without exceeding 160 degrees Celsius, morepreferably 75 or more without exceeding 140 degrees Celsius, still morepreferably 80 or more without exceeding 120 degrees Celsius. Generally,this roll temperature is set at Tg or more. The cellulose acetate filmcontaining the residual solvent tends to stick to the nip roll, and thewrinkles resulting therefrom produces uneven drawing. If the temperatureof the roll immediately before drawing is set at Tg or less, it ispossible to prevent the film from sticking to the roll.

b) To avoid uneven linear expansion coefficient, drawing is carried outwhen the spacing between drawing rolls is set preferably at 3 or morewithout exceeding 8 times the base width, more preferably at 3.5 or morewithout exceeding 7.5 times, still more preferably at 4 or more withoutexceeding 7 times. Normally, drawing is carried out with the spacing setat not more than 2 times the base width. Such a small spacing cannotprovide sufficiently molecular orientation, and therefore, cannot reducethe linear expansion coefficient sufficiently. In the present invention,to provide sufficiently strong molecular orientation and to reduce thelinear expansion coefficient, drawing is preferably carried out betweenthe rolls having the aforementioned long span.

c) The temperature at the end of the film is preferably 10 or morewithout exceeding 30 degrees Celsius lower than that at the center, morepreferably 13 or more without exceeding 27 degrees Celsius lower thanthat at the center, still more preferably 15 or more without exceeding 2degrees Celsius lower than that at the center. This arrangement reducesthe uneven drawing caused by excessive drawing force applied to the end.This method tends to produce uneven drawing especially in the transversedirection, when drawing is carried out using the aforementioned longspan. It is particularly important to perform the operation incombination therewith. To provide such temperature distribution on thefilm, a radiant heat source (IR heater and halogen heater) can be usedto heat the end alone locally, or a split heater is incorporated in thenip roller, thereby producing a temperature difference.

After drawing at a reduced tension, the film tension can be reducedwhile the film is cooled. In the cooling process, the drawingtemperature is reduced gradually using two or more steps of temperatureregulating rolls. In this case, the difference of temperatures ofadjacent rolls is preferably 50 degrees Celsius or less. If quickcooling is performed over this level, wrinkles will appear on the filmto cause uneven drawing, with the result that moisture expansioncoefficient of the film will be uneven. It is a preferred practice toreduce the peripheral speed of the temperature regulating roll at theoutlet side during this time, thereby reducing the film tension. Theamount of reducing the film tension is preferably 10 percent or less,more preferably 7 percent or less, still more preferably 5 percent orless.

If the transparent film for display to be manufactured is the celluloseester and semi-IPN polymer alloy such as cross-linked (meth)acrylate,the drawing operation is preferably carried out prior to polymerizationof a (meth)acrylate monomer. Accordingly, subsequent to drawing,activated radiation is applied for polymerization of (meth)acrylatemonomer.

As described above, the cellulose ester film wherein the amount ofplasticizer to be added is less than 1 percent is formed by casting filmmaking method, and the film is drawn both in the direction of conveyanceand in the transverse direction. This arrangement provides a transparentfilm for display substrate wherein glass-transition temperature is 180degrees Celsius and more, and thermal expansion coefficient is in therange from 5 through 50 ppm/degrees Celsius. Thus, the crystallinetransparent conductive film of low resistance can be formed on thetransparent film for display substrate of the present invention.Further, the thermal expansion coefficient is 50 ppm/degrees Celsius orless. This reduces the possible deterioration before or after theprocess of manufacturing the functional thin film such as gas barrierlayer and transparent conductive layer.

It should be added that the glass-transition temperature is 200 degreesCelsius or more and the thermal expansion coefficient is 5 through 30ppm/degrees Celsius.

<Moisture Proof Film>

To reduce the vapor transparency, the transparent film for displaysubstrate of the present invention preferably has the coatings made ofmetallic oxide, metallic nitride, metallic oxynitride and metalliccarbide formed as a moisture proof film on at least one side of thetransparent film. These coatings may be laminated or may be formed onboth sides.

In the cellulose ester film of the present invention, the amount of theplasticizer for reducing the moisture expansion coefficient is kept atas small as less than 1 percent by mass. Accordingly, the aforementionedcoatings are more preferably formed on both sides. A gas barrier isformed on both sides of the cellulose ester film. This arrangementvirtually removes the moisture absorbing capacity of the cellulose esterfilm, whereby the moisture expansion coefficient is reduced and thedisadvantages resulting from scarcity of the plasticizer are minimized.

The oxide, nitride, carbide and oxynitride composed of more than oneelement selected from the silicon, zirconium, titanium, tungsten,tantalum, aluminum, zinc, indium, chromium, vanadium, tin and niobiumcan be mentioned as the metallic oxide, metallic nitride and metallicoxynitride. Use of silicon oxide, aluminum oxide, silicon nitride andsilicon carbide are preferred, and the metallic oxide mainly composed ofsilicon oxide is particularly preferred. The term “mainly composed of”signifies that the content in the component of the moisture proof filmis 80 percent by mass or more.

The metallic oxide, metallic nitride and metallic oxynitride can beproduced, for example, by vapor deposition, sputtering and ion plating.Use of the plasma discharge method under atmospheric pressure to bedescribed later is preferred. According to the plasma CVD method underatmospheric pressure, the reaction is carried out under atmosphericpressure that is a very high pressure. Thus, the mean free path of thefine particle forming the inorganic thin film is short and a very flatfilm can be obtained, so that a high gas barrier property is ensured.

Further, as disclosed in: J. Sol-Gel Sci. Tech., P. 141 through 146(1998), the thin film of the metallic oxide, metallic nitride, metallicoxynitride and metallic carbide is susceptible to a crack, and vaporleaks from the crack. To prevent this, various types of coatingmaterials are applied onto the moisture proof film of the metallicoxide, metallic nitride and metallic oxynitride, whereby the crack issealed to reduce moisture permeability.

<Transparent Conductive Film>

The following describes the transparent conductive film:

The transparent conductive film of the present invention is commonlyknown as an industrial material. It hardly absorbs visible light (400through 700 nm) and provides a superb conductor film. The transmissioncharacteristic of the free charging member for carrying electricity ishigh in the visible light area. The film is transparent and has a highdegree of electric conductivity, and therefore, is used as a transparentelectrode for display such as the organic electroluminescence displayapparatus and liquid crystal display apparatus. When the transparentconductive film is used as the display transparent electrode, thethickness of the transparent conductive film is preferably about 100through 140 nm for the tradeoff between the film strength and surfaceresistivity.

The transparent conductive film is exemplified by a composite oxide filmcomposed of a metallic oxide film of SnO₂, In₂O₃, CdO, ZnO₂, SnO₂, Sb,SnO₂, F, ZnO, Al, In₂O₃ and Sn, and dopant.

The composite oxide film made of dopant includes the ITO film obtainedby doping tin into indium oxide, and the FTO film obtained by dopingfluorine into tin oxide, as well as the IZO film composed of In₂O₃—ZnOamorphous substance.

Such a transparent conductive film can be formed by the wet type filmformation method represented by coating method, or the dry type filmformation method such as sputtering, vapor deposition and ion plating,for example. To form a transparent conductive film on the conductivefilm of the present invention, a plasma discharge method underatmospheric pressure characterized by a simple film making process ispreferably used.

<Plasma Discharge Method Under Atmospheric Pressure>

In the plasma discharge method under atmospheric pressure, an electricfield is produced between opposing electrodes under atmospheric pressureor under pressure close to atmospheric pressure so that the reactive gasbetween the electrodes is formed in a state of plasma. Then thesubstrate is exposed to the reactive gas in the state of plasma, wherebya film is formed on the substrate.

In the present invention, the pressure close to atmospheric pressuredenotes the pressure from 20 through 110 kPa. Use of 93 through 104 kPais preferred.

The following describes an example of the apparatus and method forplasma discharging under atmospheric pressure wherein the transparentconductive film of the present invention is formed on the celluloseester film of the present invention (hereinafter referred to as“substrate film”).

<The Plasma Discharge Apparatus Under Atmospheric Pressure>

The plasma discharge apparatus under atmospheric pressure has a rollelectrode as a ground electrode and a plurality of fixed electrodes asapplicators arranged at an opposed position. Discharging is carried outbetween these electrodes so that the inert gas introduced between theseelectrodes and the reaction gas containing reactive gas are formed in astate of plasma. The substrate film rotated and fed by the rollelectrode is exposed to the reaction gas in the state of plasma, wherebya moisture proof film and conductive film are formed on the film.

According to a jetting method, the substrate film is placed close to theelectrode—not between electrodes—, and is fed. The plasma havingoccurred is blown onto the substrate film so that a thin film is formed.

FIG. 1 is a drawing representing an example of the plasma dischargeapparatus under the atmospheric pressure of the present invention or thepressure close to it. The apparatus in FIG. 1 is composed of a plasmadischarge apparatus 30, a gas charging section 50, a voltage applicationsection 40, an electrode temperature regulating section 60. A rollrotating electrode 35 and rectangular fixed electrode group 36 are usedfor plasma discharging of the substrate film CF. The substrate film CFis unwound from the master roll (not illustrated) and is fed.Alternatively, the substrate film CF is fed from the previous steppasses through a guide roll 64. Air and others entrained by thesubstrate film is blocked by the nip roll 65. The film is wound androtated in contact with the roll rotating electrode 35 and is fedbetween the rectangular fixed electrode group 36. It goes through a niproll 66 and a guide roll 67 and is wound up by a winder (notillustrated) to be fed to the next step. A gas charging section 50controls the flowrate of the reaction gas G generated from the gasgenerator 51, and the gas is fed into the plasma discharge container 31of a discharge chamber 32 through the air inlet 52, so that the plasmadischarge container 31 is filled with the reaction gas G. The waste gasG′ is removed from the exhaust port 53. Then voltage is applied to therectangular fixed electrode group 36 by the voltage application section40 through a high frequency power source 41. The roll rotating electrode35 is grounded by means of a wire, and a discharge plasma is producedbetween electrodes. The electrode temperature regulating section 60heats or cools the liquid medium and sends into the roll rotatingelectrode 35 and rectangular fixed electrode group 36. The medium thetemperature of which has been regulated by the electrode temperatureregulating section 60 is fed through a pipe 61 by a liquid feed pump P,and the temperature is controlled from inside the roll rotatingelectrode 35 and rectangular fixed electrode group 36.

The physical properties and composition of the thin film obtained fromthe temperature of the substrate film may be subjected to change at thetime of plasma discharging. Adequate measures should be taken to controlthis change. Such an insulating material as distilled water and oil ispreferably used as the medium. In the step of plasma discharging, thetemperature inside the rotating electrode using a roll is preferablycontrolled in order to avoid the uneven temperature of the substratefilm in the transverse or longitudinal direction. It should be addedthat numerals 68 and 69 indicate a partition plate for separating theplasma discharge container 31 and the outside world.

The reaction gas used for discharging plasma is led to the plasmadischarge container 31 from the air inlet 52. After processing, the gasis discharged from the exhaust port 53.

FIG. 2 is a sketch representing an example of the structure of theconductive base material of the metal of a roll electrode or the likeand the dielectric covering the same.

In FIG. 2, the roll rotating electrode 35 a as a ground electrode is acombination structure coated with a ceramic-coated dielectric 35Bprovided with pore sealing treatment using the pore sealing material ofan inorganic compound, subsequent to spraying of a ceramic, as andielectric coated layer for the conductive base material 35A. It iscoated with the ceramic coated dielectric with a thickness of 1 mm onone side, and is connected to the ground. Alumina/silicon nitride andothers are preferably used as the ceramic material used for spraying. Inparticular, alumina is more preferably used because it is characterizedby easy processing.

The lined dielectric equipped with an inorganic material by a glasslining can be used as the dielectric layer.

The conductive base material 35A of metal or the like includes: metalssuch as titanium metal, titanium alloy, silver, platinum, stainlesssteel, aluminum and iron, and a composite material between iron andceramic; and a composite material between aluminum and ceramic. From theviewpoint of electrode stability, titanium metal or titanium alloy ispreferably used.

The details of the conductive base material and dielectric will bedescribed later.

FIG. 3 is a sketch representing an example of the structure of the basematerial of the rectangular fixed electrode as an applicator wherein oneof the rectangular fixed electrode group has been picked up, and thestructure of the dielectric covering the same.

In FIG. 3, the rectangular electrode group 36 a has the same dielectriccoating layer as that shown in FIG. 2, for the conductive base materialsuch as a metal. To be more specific, the same dielectric as the aboveis coated on the hollow metallic pipe. Cooling by cooling water can bemade during the discharging operation. Fourteen rectangular fixedelectrodes are installed along the circumference greater than that ofthe roll electrode.

The rectangular electrode shown in FIG. 3 has the effect of increasingthe range of discharge (discharge range) as compared to the cylindricalelectrode, and is preferably used according to the thin film formingmethod of the present invention.

There is no particular restriction to the power source for applyingvoltage to the applicator. It is also possible to the power source foroscillating the high frequency power source (3 kHz) by Shinko ElectricCo., Ltd., high frequency power source (5 kHz) by Shinko Electric Co.,Ltd., high frequency power source (15 kHz) by Shinko Electric Co., Ltd.,high frequency power source (50 kHz) by Shinko Electric Co., Ltd.,frequency variable high frequency power source by Heiden ResearchInstitute (continuous mode (2.5 through 100 kHz), high frequency powersource by Pearl Industry Co., Ltd. (200 kHz), high frequency powersource by Pearl Industry Co., Ltd. (80 kHz), high frequency power sourceby Pearl Industry Co., Ltd. (2 MHz), high frequency power source byNippon Electric Co., Ltd. (13.56 MHz), high frequency power source byPearl Industry Co., Ltd. (27 MHz) and high frequency power source byPearl Industry Co., Ltd. (150 MHz). It is also possible to use the powersource for oscillating 433 MHz, 800 MHz, 1.3 GHz, 1.5 GHz, 1.9 GHz, 2.45GHz, 5.2 GHz and 10 GHz. There may be a difference in the frequencycapable of exciting the molecular in the mixed gas, and therefore, twoor more frequencies can be superimposed. The preferred combination inthis case is the superimposition of a 1 kHz through 1 MHz power sourceand a 1 MHz through 2.5 GHz power source.

The distance between the aforementioned electrodes is determined withconsideration given to the thickness of the solid dielectric provided onthe conductive base material of the electrode, the magnitude of theapplied voltage and the purpose of using the plasma. The shortestdistance between the surface of the dielectric and the electrode whenone of the aforementioned electrodes is equipped with the dielectric,and the distance between the surfaces of the dielectrics when both ofthe aforementioned electrodes are equipped with dielectrics arepreferably 0.5 through 20 mm in either case, preferably in particular1±0.5 mm, from the viewpoint of ensuring uniform discharging.

The voltage value applied by the power source 41 to the rectangularfixed electrode group 36 is determined as appropriate. For example, whenthe voltage is about 10 through 10 kV, the power source frequency isadjusted to more than 100 kHz without exceeding 150 MHz. For the powersource application method, either the continuous sine waveformcontinuous oscillation mode called the continuous mode, or theintermittent oscillation mode for intermittent ON/OFF operation calledthe pulse mode can be selected. However, the continuous mode willprovide a more compact and higher-quality film.

A pyrex (R) glass-made processing vessel is preferably used as theplasma discharge container 31. If insulation with the electrode can besecured, use of the metallic product is also possible. For example, aninner surface of the aluminum or stainless steel frame may be lined witha polyimide resin. Ceramic spraying may be applied to the metallic frameto provide insulation.

Further, to minimize impact on the substrate film in the step ofdischarge plasma processing, the temperature of the substrate film inthe step of discharge plasma processing is preferably adjusted withinthe range from the normal temperature (15 through 25 degrees Celsius) to300 degrees Celsius. For adjustment within the aforementioned range, theelectrode and substrate film is subjected to discharge plasma processingwhile being cooled or heated by a temperature adjusting device, ifrequired.

<Reaction Gas>

The following describes the reaction gas for forming a moisture prooffilm on the transparent film for display substrate of the presentinvention. The reaction gas to be used is basically composed of an inertgas and a reactive gas for forming a thin film.

The reaction gas to be used is a gas mixture containing an inert gas andreactive gas. The inert gas is a Group 18 element in the Periodic Table.To put it more specifically, it includes a rare gas such as helium,neon, argon, krypton, xenon and radon, or nitrogen. To get theadvantages of the present invention, helium, argon and nitrogen arepreferably used. To form a compact and high-quality thin film, use ofargon as a rare gas is most preferred. It can be estimated thathigh-density plasma is generated more easily if argon is used. 90.0through 99.0 percent by volume of argon gas is preferably contained withrespect to 100 percent by volume of a reaction gas (gas mixture composedof a rare gas and reactive gas).

To form a moisture proof thin film, the reaction gas to be used isbasically composed of an inert gas and a reactive gas for forming a thinfilm. 0.01 through 10 percent by volume of reactive gas is preferablycontained with respect to the reaction gas. The thin film having athickness from 0.1 through 1,000 nm is obtained.

The reactive gas is formed in a state of plasma in the discharge space,and contains:

the components for forming a thin film, which include the compounds forforming a thin film such as an organic metallic compound, organiccompound, inorganic compound; and optionally,

gases for supplementary use such as hydrogen gas, oxygen gas and carbondioxide.

<Reactive Gas for Forming a Moisture Proof Film>

Any compound can be used as the reactive gas for forming a moistureproof film if it is capable of providing an adequate moisture proofproperty. A titanium compound, tin compound, silicon compound, fluorinecompound, silicon compound containing fluorine or a mixture of thesecompounds can be used preferably. Of them, the silicon compound is mostpreferably used.

It can be a gas a liquid and a solid under normal temperature and normalpressure. When it is a gas, it can be introduced directly into thedischarge space. If it is a liquid or a solid, it is turned into a gasby heating, bubbling, pressure reduction, ultrasonic irradiation or thelike before it is used. Further, it can be used after being diluted by asolvent. In this case, an organic solvent such as methanol, ethanol andn-hexane and the solvent mixture thereof can be used as the solvent.Such a diluted solvent in the plasma discharge processing is decomposedinto molecules and atoms, and therefore, their impact can be ignoredalmost completely.

However, it is preferably a compound having a vapor pressure in thetemperature range of 0 through 250 degrees Celsius under atmosphericpressure, more preferably a compound in a liquid state in thetemperature range of 0 through,250 degrees Celsius. This is because thepressure in the plasma film making chamber is close to the atmosphericpressure, and a gas can be introduced in the plasma film making chamberonly under the atmospheric pressure. Further, when the material compoundis in a state of liquid, the amount to be introduced into the plasmafilm making chamber can be placed under more accurate control.

Compounds containing silicon as one of such organic metallic compoundsare exemplified by: silane, tetramethoxysilane, tetraethoxysilane, tetran-propoxysilane, tetraisoproxysilane, tetra n-butoxysilane, tetrat-butoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane,diethyldimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane,ethyltrimethoxysilane, phenyltriethoxysilane,(3,3,3-trifluoropropyl)trimethoxysilane, hexamethyldisiloxane,hexamethylcyclotrisiloxane, tetramethylcyclotetrasiloxane,octamethylcyclotetrasiloxane, bis(dimethylamino)dimethylsilane,bis(dimethylamino)methylvinylsilane, bis(ethylamino)dimethylsilane,N,O-bis(trimethylsilyl)acetoamido, bis(trimethylsilyl)carbodiimide,diethylaminotrimethylsilane, dimethylaminodimethylsilane,hexamethyldisilazane, hexamethylcyclotrisilazane, heptamethyldisilazane,nonamethyltrisilazane, octamethylcyclotetrasilazane,tetrakisdimethylaminosilane, tetraisocyanatesilane,tetramethyldisilazane, tris(dimethylamino)silane, triethoxyfluorosilane,allyldimethylsilane, allyltrimethylsilane, benzyltrimethylsilane,bis(trimethylsilyl)acetylene, 1,4-bistrimethylsilyl-1,3-butadiene,di-t-butylsilane, 1,3-disilabutane, bis(trimethylsilyl)methane,cyclopentadienyltrimethylsilane, phenyldimethylsilane,phenyltrimethylsilane, propargyltrimethylsilane, tetramethylsilane,trimethylsilylacetylene, 1-(trimethylsilyl)-1-propyne,tris(trimethylsilyl)methane, tris(trimethylsilyl)silane,vinyltrimethylsilane and hexamethyldisilane.

The compounds containing titanium are exemplified by: titaniummethoxide, titanium ethoxide, titanium isopropoxide, titaniumn-butoxide, titanium diisopropoxide(bis-2,4-pentanedionate), titaniumdiisopropoxide(bis-2,4-ethylacetoacetate), titaniumdi-n-butoxide(bis-2,4-pentanedionate), titanium acetylacetonate, andbutyl titanate dimer.

The compounds containing zirconium are exemplified by: zirconiumn-propoxide, zirconium n-butoxide, zirconium t-butoxide, zirconiumtri-n-butoxideacetylacetonate, zirconiumdi-n-butoxidebisacetylacetonate, zirconium acetylacetonate, zirconiumacetate, and zirconium hexafluoropentanedionate.

The compounds containing aluminum are exemplified by: aluminum ethoxide,aluminum isopropoxide, aluminum n-butoxide, aluminum s-butoxide,aluminum t-butoxide, aluminum acetylacetonate, triethyldialuminumtri-s-butoxide, and trimethylamine-alane.

The compounds containing boron are exemplified by: diborane,tetraborane, boron fluoride, boron chloride, boron bromide,borane-diethylether complex, borane-THF complex, borane-dimethylsulfidecomplex, boron trifluoride diethyl ether complex, triethyl borane,trimethoxyborane, triethoxyborane, tri(isopropoxy)borane, borazol,trimethylborazole, triethylborazole, and triisopropylborazole.

The compounds containing tin are exemplified by: tetraethyl tin,tetramethyl tin, diacetate di-n-butyl tin, tetrabutyl tin, tetraoctyltin, tetraethoxy tin, methyltriethoxy tin, diethyldiethoxy tin,triisopropylethoxy tin, diethyl tin, dimethyl tin, diisopropyl tin,dibutyl tin, diethoxy tin, dimethoxy tin, diisopropoxy tin, dibutoxytin, tin dibutyrate, tin diacetoacetonate, ethyl tin acetoacetonate,iethoxy tin acetoacetonate and other such related dimethyl tindiacetoacenate. The tin hydrogen compound is exemplified by halogenatedtin dichloride and tin tetrachloride.

The compounds made of other metals are exemplified by: antimonyethoxide, arsenic triethoxide, barium 2,2,6,6-tetramethylheptanedionate,beryllium acetylacetonate, bismuth hexafluoropentanedionate,dimethylcadmium, calcium 2,2,6,6-tetramethylheptanedionate, chromiumtrifluoropentanedionate, cobalt acetylacetonate, copperhexafluoropentanedionate, magnesiumhexafluoropentanedionate-dimethylether complex, gallium ethoxide,tetraethoxygermane, tetramethoxygermane, hafnium t-butoxide, hafniumethoxide, indium acetylacetonate, indium2,6-dimethylaminoheptanedionate, ferrocene, lanthanum isopropoxide, leadacetate, tetraethyl lead, neodymium acetylacetonate, platinumhexafluoropentanedionate, trimethylcyclopentanedienyl platinum, rhodiumdicarbonylacetylacetonate, strontium 2,2,6,6-tetramethylbutanedionate,tantalum methoxide, tantalum trifluoroethoxide, tellurium ethoxide,tungsten ethoxide, vanadium triisopropoxide oxide, zinc acetylacetonate,diethyl zinc and diethyl zinc.

Of these metallic compounds, the silicon compound can be preferably usedas the reactive gas. The silicon compound is safe, non-explosive andhighly volatile, and therefore, a stable supply of the silicon compoundis possible in a plasma space, thereby ensuring homogeneous filmformation.

The surface specific resistance of the tin oxide layer and zinc oxidelayer composed of a tin compound and zinc compound can be reduced below10¹¹ Ω/cm², and provide the functions of both a moisture proof film anda antistatic layer. Thus, the tin compound and zinc compound arepreferable reactive gases.

<Reactive Gas for Forming a Transparent Conductive Film>

The reactive gas for forming a transparent conductive film used to forma transparent conductive film by atmospheric pressure plasma processingmethod is formed in a state of plasma in a discharge space, and containsthe component for forming a transparent conductive film. An organicmetallic compound such as β-diketone metallic complex, metallic alkoxideand alkyl metal is used. The reactive gas is available in two types; areactive gas as a major component of the transparent conductive film,and a reactive gas, a small amount of which is used for doping. There isalso a reactive gas used to adjust the resistance of the transparentconductive film.

The organic metallic compound having an oxygen compound in the moleculeis preferably used is the reactive gas used as a major component in theformation of the transparent conductive film. Examples include: indiumhexafluoropentanedionate, indium methyl(trimethyl)acetylacetonate,indium acetylacetonate, indium isopropoxide, indiumtrifluoropentanedionate,tris(2,2,6,6-tetramethyl-3,5-heptanedionate)indium, pentanedienylindium,di-n-butylbis(2,4-pentanedionate)tin, di-n-butyldiacetoxy tin,di-t-butyldiacetoxy tin, tetraisopropoxy tin, tetrabutoxy tin and zincacetylacetonate. Of these examples, particularly preferred ones are:indium acetylacetonate, tris(2,2,6,6-tetramethyl3,5-heptanedionate)indium, zinc acetylacetonate and di-n-butyldiacetoxytin.

The reactive gas used for doping includes: aluminum isopropoxide, nickelacetylacetonate, manganese acetylacetonate, boron isopropoxide, n-butoxyantimony, tri-n-butylantimony, di-n-butylbis(2,4-pentanedionate)tin,di-n-butyldiacetoxy tin, di-t-butyldiacetoxy tin, tetraisopropoxy tin,tetrabutoxy tin, tetrabutyl tin, zinc acetylacetonate, pentafluoridepropylene, hexafluoridecyclobutane and tetrafluoridecyclobutane.

The reactive gas used for adjustment of the resistance of thetransparent conductive film includes titanium triisopropoxide,tetramethoxysilane, tetraethoxysilane, and hexamethyldisiloxane.

The quantitative ratio between the reactive gas used as a majorcomponent of the transparent conductive film and the reactive gas, asmall amount of which is used for doping, varies according to the typeof the transparent conductive film to be formed. For example, the amountof the reactive gas is adjusted so that the ratio in the numbers ofatoms between In and Sn of the ITO film obtained by doping the indiumoxide with tin is 100/0.1 through 100/15, preferably 100/0.5 through100/10. The ratio in the numbers of atoms between In and Sn can beobtained from the XPS measurement.

The quantitative ratio of the reactive gas is adjusted so that the ratioin the numbers of atoms between Sn and F of the FTO film obtained bydoping the tin oxide with fluorine is 100/0.01 through 100/50. The ratioin the numbers of atoms between Sn and F can be obtained from the XPSmeasurement.

In the In₂O₃—ZnO amorphous transparent conductive film (IZO film), thequantitative ratio of the reactive gas is adjusted so that the ratio inthe number of atoms between In and Zn is 100/50 through 100/5. The ratioin the numbers of atoms between In and Zn can be obtained from the XPSmeasurement.

In the aforementioned ITO, FTO and IZO films, the amount of Sn dope, forexample, is preferably 5 percent by mass or less.

To ensure uniform formation of film on the substrate film by dischargeplasma processing, the content of these reactive gases in the reactiongas is preferably 0.01 through 10 percent by volume, more preferably0.01 through 1 percent by volume.

Further, if 0.01 through 5 percent by volume of a component selectedfrom among the oxygen, ozone, hydrogen peroxide, carbon dioxide, carbonmonoxide, hydrogen and nitrogen is contained in the reactive gas,reaction will be promoted to produce a compact and high-quality thinfilm.

The transparent conductive film having a thickness of 0.1 nm through1,000 nm is provided.

To introduce the aforementioned organic tin compound, organic titaniumcompound, organic silicon compound, organic zinc compound or organicindium compound between the electrodes forming a discharge space, thetwo compounds can be in any of the states of gas, liquid and solid atthe normal temperature and pressure. If they are in a state of gas, theycan be introduced directly into the discharge space. If they are in astate of liquid or solid, they are turned into a gas by heating,pressure reduction, ultrasonic irradiation or the like before they areused. Further, the aforementioned metallic alkoxide can be used afterbeing diluted by a solvent. In this case, it is gasified in the rare gasby a vaporizer before it is used as a reaction gas. Such an organicsolvent as an organic solvent such as methanol, ethanol isopropanol,butanol and n-hexane or the solvent formed by the mixture thereof can beused as the solvent.

<Applied Voltage>

It is preferred that, in the thin film forming method based onatmospheric pressure plasma processing, a power of 1 W/cm² or more(output density) with a high-frequency voltage exceeding 100 kHz besupplied across the electrodes arranged opposite to each other, and thereactive gas is excited so that the plasma is produced.

The upper limit of the frequency of the high-frequency voltage to beapplied across the electrodes is preferably 2.5 GHz, more preferably 150MHz. The lower limit of the frequency of the high-frequency voltage tobe applied across the electrodes is preferably 200 kHz, more preferably800 kHz. If the high-frequency voltage is smaller than 100 kHz, the filmmaking speed will be reduced, with the result that productivity will bereduced in some cases.

The lower limit value of the power supplied across the electrodes ispreferably 1 W/cm². The upper limit value is preferably 50 W/cm², stillmore preferably 20 W/cm². If the power is smaller than 1 W/cm², the filmmaking speed will be reduced, with the result that productivity will bereduced in some cases. The discharge area (1/cm²) denotes the area inthe range wherein discharge occurs in the electrode. If a high powervoltage with a high frequency and high output density is applied as inthe present invention, the discharge area corresponds to the dischargearea of one of the electrodes. If the total power (W) supplied from thepower source connected to the aforementioned electrodes is divided bythis total area, the output density can be calculated.

Further, in the atmospheric pressure plasma processing method in orderto get a uniform film thickness in a large area in particular, the totalpower applied to a pair of opposing electrode is preferably over 15 kW,more preferably 30 kW, or more still more preferably 50 kW or more. Fromthe viewpoint of heat generation, it is preferably 300 kW or less. Thetotal power corresponds to the power (W) supplied from the power sourceconnected to the aforementioned set of electrodes. When two or morepower sources are connected to the aforementioned set of electrodes, itcorresponds to the total of the powers supplied from all of these powersources. To put it more specifically, in the atmospheric pressure plasmaprocessing apparatus given in FIG. 1, it corresponds to the powersupplied from the power source 41 connected therewith wherein the rollrotating electrode 35 and rectangular fixed electrode group 36 are a setof opposing electrodes. To meet the requirements of the total powerrange, the discharge area is required to have a size over a certainvalue.

Further, the high-frequency voltage applied across the electrodes can bean intermittent pulse wave or continuous sine wave. To make an effectiveuse of the advantages of the present invention, a continuous sine waveis preferred.

<Electrode>

As the electrode used for atmospheric pressure plasma processing, theplasma discharge processing apparatus is required to adopt ahigh-durability electrode capable of maintaining a uniform state ofdischarge even if such a high-power electric field is applied to theelectrode having a large area under atmospheric pressure or under thepressure close to the under atmospheric pressure.

In such an electrode, at least the discharge surface of the conductivebase material such as a metal is coated with a dielectric. Preferably,both the application electrode and ground electrode are coated with thedielectric.

The electrode coated with dielectric is a composite component made up ofa conductive base material such as a metal, and a dielectric materialsuch as ceramic and glass. If the power to be supplied, especially thetotal power, is great, fracture tends to start to occur from the brittleportion of the dielectric. This makes it difficult to ensure plasmadischarge stability. Especially in the dielectric-coated electrodehaving a large discharge area, this disadvantage is conspicuous. Toimplement the thin film formation method of the present invention, atleast one of the electrodes is required to be a dielectric-coatedelectrode capable of overcoming the aforementioned difficulties.

To put it more specifically, the dielectric used in thedielectric-coated electrode of the present invention is preferably aninorganic compound having a relative dielectric constant of 6 through45. Such a dielectric includes a ceramic sprayed material such asalumina and silicon nitride, or a glass lined material such as silicateglass and borate glass. Of these materials, the ceramic sprayed materialor glass lined material (to be described later) are preferably used.Especially the alumina-sprayed dielectric is preferred.

The preferred dielectric coated electrode capable of withstanding highpower has a heat resistance temperature 100 degrees Celsius or more,preferably 120 degrees Celsius or more, more preferably 150 degreesCelsius or more. The heat resistance temperature refers to the highesttemperature to be endured under normally dischargeable conditions,without dielectric breakdown. Such a heat resistance temperature can beobtained by application of the aforementioned ceramic spayed material orglass lined material of laminated structure, or by adequate combinationof the means for adequate selection of the material within the range ofthe difference in linear thermal expansion coefficients between thefollowing conductive base material and dielectric.

In the dielectric coated electrode used in the present invention,another preferred example is such a combination that the difference inlinear thermal expansion coefficient between the dielectric andconductive base material is 10×10⁻⁶/degrees Celsius or less, preferably8×10⁻⁶/degrees or less, more preferably 5×10⁻⁶/degrees or less, stillmore preferably 2×10⁻⁶/degrees or less. The linear thermal expansioncoefficient is defined as a physical property specified to a knownmaterial.

A preferred combination of the conductive base material and dielectricwherein the difference in linear thermal expansion coefficient is withinthis range is such a combination that the conductive base material is atitanium metal or titanium alloy containing 70 percent by mass or moreof titanium, and the dielectric is a ceramic-sprayed film or a glasslined film.

The aforementioned titanium metal or alloy can be used without problem,if it contains not less than 70 percent by mass of titanium. It ispreferred to contain 80 percent by mass of titanium. The titanium metalor alloy applicable to the present invention includes the one commonlyused as pure titanium for industrial use, corrosion proof titanium andhigh strength titanium. The pure titanium for industrial use includesTIA, TIB, TIC and TID. They each contain a very small amount of ironatom, carbon atom, nitrogen atom, oxygen atom, and hydrogen atom, andcontain not less than 99 percent by mass of titanium. The T15PB ispreferably used as the corrosion proof titanium alloy. In addition tothe aforementioned atoms, it contains lead. The titanium content is notless than 98 percent by mass. Further, the T64, T325, T525 and TA3containing aluminum, vanadium and tin in addition to the aforementionedatoms except for the lead in addition to the aforementioned atoms exceptfor the lead is preferably used as a titanium alloy. The titaniumcontent of some of them is not less than 85 percent by mass. Thesetitanium alloy or metal has a thermal expansion coefficient of about ½smaller than that of the stainless steel, for example, AISI316. Acombination with the dielectric (to be described later) provided on thetitanium alloy or metal is preferred as a metallic base material,because it allows a long-time use at a high temperature.

Another requirement of the dielectric coated electrode of the presentinvention capable of withstanding high power is that the dielectric hasa thickness of 0.5 through 2 mm. The variation in the film thickness ispreferably 5 percent or less, more preferably 3 percent or less, stillmore preferably 1 percent or less.

To further reduce the void ratio of the dielectric, the ceramic sprayedfilm or the like is preferably provided with pore sealing, using aninorganic compound. The inorganic compound is preferred to be a metaloxide. The metal oxide containing the silicon oxide (SiO₂) as a majorcomponent is preferred in particular.

The inorganic compound provided with pore sealing treatment ispreferably cured and formed by sol-gel reaction. If the inorganiccompound provided with pore sealing treatment is mainly composed of themetal oxide, the metallic alkoxide as the pore sealing solution iscoated on the ceramic sprayed film, and is cured by sol-gel reaction. Ifthe inorganic compound is mainly composed of silica, alkoxysilane ispreferably used as the pore sealing solution.

To promote the so-gel reaction, use of energy processing is preferred.The method of energy processing includes heat curing (preferably at 200degrees Celsius or less) and ultraviolet irradiation. In the step ofpore sealing, the pore sealing solution is diluted, and coating andcuring operations are repeated several times in sequence. This willfurther improve the purity of the inorganic content, and will produce acompact electrode free of deterioration.

In the case of pore sealing treatment wherein the metallic alkoxide orthe like of the dielectric coated electrode as a pore sealing solutionis coated on the ceramic sprayed film, and curing is carried out byso-gel reaction, the content of the metal oxide having been cured ispreferably 60 mol percent or more. When alkoxysilane is used as themetallic alkoxide of the pore sealing solution, the content of theSiO_(x) having been cured (x denotes 2 or less) is preferably 60 molpercent or more. The content of SiO_(x) having been cured can bemeasured by analyzing the cross section of the dielectric layer by XPS.

The surface roughness Rmax (JIS B 0601) of the electrode can be kept at10 μm or less by grind-finishing the surface of the dielectric of thedielectric coated electrode. This procedure ensures a constant thicknessof the dielectric and a constant gap between electrodes, and improvesthe stability of discharging. Further, this procedure eliminates thedifference in thermal shrinkage, and the strain and crack resulting fromresidual stress, and ensures higher precision and much improveddurability. Grind-finishing if the surface of the dielectric ispreferably applied to the dielectric on the side in contact with thesubstrate film.

<Activated Light Curable Resin>

A metallic compound such as the moisture proof film and transparentconductive film can be directly formed on the aforementioned transparentfilm for display substrate of the present invention. Alternatively, themetallic compound can be formed on at least one other intermediate layerprovided on the aforementioned transparent film. An antiglare layer orclear hard core is preferably used as such a layer to be provided. Themoisture proof film and transparent conductive film of the presentinvention are formed on the resin layer cured by ultraviolet rays,whereby a transparent conductive film characterized by excellentresistance to a scratch is obtained.

When the metal oxide is formed by atmospheric pressure plasmaprocessing, this intermediate layer improves bondability and reducesplasma damages. Thus, the intermediate layer improves thecharacteristics of the metallic compound layer, as compared to the casewhere metallic compound is formed directly on the transparent film ofthe present invention. The intermediate layer improves the degree ofadhesion between the transparent film of the present invention and themetallic compound.

The activated light cured resin layer such as an antiglare layer and aclear hard core is a resin layer formed by polymerization of thecomponent including the polymerizable unsaturated monomer. The activatedlight cured resin layer is defined as a layer mainly composed of theresin cured through cross-linking reaction and others by irradiation ofthe activated light such as an ultraviolet ray and electron beam. Theactivated light cured resin layer is typically represented by theultraviolet cured ink and electron beam cured resin. It is also possibleto use the resin that is cured by the light other than ultraviolet curedink and electron beam. The ultraviolet cured resin includes ultravioletcured type acryl urethane resin, ultraviolet cured type polyesteracrylate resin, ultraviolet cured type epoxy acrylate resin, ultravioletcured type polyol acrylate resin and ultraviolet cured type epoxy resin.

<Layer Composition>

In the display substrate wherein a moisture proof film or transparentconductive film having a small thickness is formed on the transparentfilm for display substrate, these layers can be laminated one on top ofanother. Alternatively, they can be formed on each surface of thesubstrate. Alternatively, the moisture proof film can be formed on bothsurfaces.

When the moisture proof film and transparent conductive film arelaminated, for example, two plasma discharge processing apparatus arearranged in a reaction gas atmosphere under atmospheric pressure orunder the pressure close to the under atmospheric pressure. They arearranged in series in the order of moisture proof film and conductivefilm so that two layers are laminated; then continuous processing can beperformed, as shown in FIG. 1. This method of continuous laminationensures stable quality, reduced cost and improved productivity, andtherefore, is suited for the production of the conductive film of thepresent invention. Needless to say, instead of simultaneous lamination,sequential processing is also possible, wherein, the processed layer iswound after processing of each layer.

A stain-proofing layer may be provided on the back of the transparentfilm for display substrate without the conductive layer laminatedthereon. If the back surface is also provided with a moisture prooffilm, a stain-proofing layer and an antireflection film can be laminatedon the moisture proof film. The transparent film or transparentconductive film of the present invention may be laminated on anotherfilm-, sheet- or plate-shaped mold.

To ensure that the visibility of a transmitted image will not beinterrupted by a stain deposited on the transparent substrate surface,the stain-proofing layer is provided to prevent a stain or fingerprintfrom being deposited, and to allow easy removal of the stain by wiping.To form a stain-proofing layer, for example, isopropyl alcohol is addedto a thermal cross-linked fluorine-containing polymer, and 0.2 percentby mass of coarsely dispersed solution is prepared. This is coated onthe surface of the extreme surface layer by a bar coater, whereby thestain-proofing layer is formed.

The following describes an example of the preferred structure of adisplay substrate of the present invention:

(A) Transparent film for display substrate of the present invention(substrate), intermediate layer, moisture proof layer and transparentconductive film

(B) Stain-proofing layer, transparent film for display substrate of thepresent invention (substrate), intermediate layer, moisture proof layerand transparent conductive film.

(C) Moisture proof layer, intermediate layer, transparent film fordisplay substrate of the present invention (substrate), intermediatelayer and transparent conductive film

(D) Stain-proofing layer, moisture proof layer, intermediate layer,transparent film for display substrate of the present invention(substrate), and transparent conductive film

<Waveform Dispersion Characteristic of Transparent Birefringence>

In the transparent film for display substrate wherein moisture prooffilm or transparent conductive film are formed, the overall lighttransmittance of the film is preferably 50% or more. In the filmgenerally used for optical application, the overall light transmittanceof the film is preferably 80% or more, more preferably 90% or more. Theoverall light transmittance can be defined as the percentage of theoverall light transmittance relative to the parallel incoming luminousflux of a test piece (See JIS K-7361-1).

In the transparent film for display substrate wherein a moisture prooffilm or transparent conductive film is formed, the waveform dispersioncharacteristic of birefringence as viewed from the normal line ispreferably positive. The polarization can be corrected in the fullwavelength area of visible light by using a film having a positivewaveform dispersion characteristic of birefringence as the displaysubstrate. In the liquid crystal panel using the display method based onthe birefringence, color misregistration is prevented. In the organicelectroluminescence display device, excellent contract is provided.

Various types of functional thin films can be laminated on thetransparent conductive film, using the transparent conductive film as athin film transparent electrode and patterning it if required, wherebysuch an electric device as the aforementioned liquid crystal display,organic electroluminescence display or touch panel is provided.

Embodiment

The following provides a specific description of the present inventionwith reference to embodiments, without the prevent invention beingrestricted thereto.

Embodiment 1

<Example of Synthesis 1>

Synthesis was carried out by reference to the synthesis method disclosedin the J. Appl. Polym. Sci., vol. 58, 1263-1274(1995).

100 parts by mass of diacetyl cellulose (hereinafter referred to as“DAC”) was dissolved in 700 parts by mass of dehydrated tetrahydrofuran(hereinafter referred to as “THF”). After that, 10 parts by mass of3-isocyanatepropylethoxysilane (hereinafter referred to as “IPTES”) wasdropped, and 0.8 parts by mass of dibutyl tin dilaurate was dropped as acatalyst. This was stirred under heating and reflex for five hours.

Five hours later, the infrared absorption spectrum of the solution wasmeasured. It was revealed that the absorption of 2271 cm⁻¹ derived fromthe isocyanate group of the IPTES had been disappeared. Accordingly,heating was suspended and the solution was left to cool down. It waspoured into 3 L of methanol to be settled again, whereby a white solidwas obtained at a yield of 99.6%. The Si²⁹⁻NMR spectrum of the whitesolid having been obtained was measured, and a single absorption wasobserved at −45.25 ppm. Further, the C¹³ —NMR spectrum was measured andthe absorption of amidocarbonyl was observed at 163.07 ppm. This hasproven that the cellulose ester 1 as a target substance was obtained.

The degree of substitution of the cellulose ester 1 having beenobtained-was-measured according to the ASTM D817-96. The following wasobtained: Acetyl group=2.33 and triethoxysilylpropylamidocarbonylgroup=0.10.

<How to Produce the Substrate Film 101 of the Present Invention>

60 parts by mass of ethanol, 685 parts by mass of methylene chloride and100 parts by mass of DAC were put in a mixing tank. They were dissolvedby being heated and stirred at 80 degrees Celsius to yield dope A.

When molecular weight was measured under the aforementioned conditions,the number average molecular weight of DAC was 120,000 and the numberaverage molecular weight was 300,000.

This dope was cast using a band caster, and was separated from off theband. Immediately thereafter, it was fed to the tenter, where it wasdrawn 10% in the TD direction and 10% in the MD direction. After that,it was dried at 120 degrees Celsius to get the substrate film 101 of thepresent invention. Coating was made in such a way as to ensure that thefilm thickness would be 100 μm in the final stage. The followingdescribes specific conditions for drawing in the longitudinal andlateral directions:

Lateral Drawing

After the film was preheated at 80 degrees Celsius for 10 seconds, itwas drawn with such a temperature gradient as to ensure that thetemperature would be 130 degrees Celsius at the termination of drawingoperation. The drawing speed was 100%/minute. A tenter rail was expandedat the drawing startup portion so that a curvature radius would be 100mm at the time of transition from preheating to drawing. After drawing,the film was loosened 5 percent at 130 degrees Celsius for 30 seconds.Drawing operation was conducted so that a predetermined magnificationwould be reached under this condition.

After that, both ends of the film having been gripped by a chuck wereslit.

Longitudinal Drawing

After the film was preheated at 90 degrees Celsius for 10 seconds, itwas passed between the rolls, having been heated up to 90 degreesCelsius, immediately before drawing. The film was drawn while beingheated by an infrared heater split in three pieces across the width, sothat the temperature at the center of the film would be 130 degreesCelsius and the temperature at both ends would be 145 degrees Celsius.Settings were determined to ensure that the value obtained by dividingthe drawing roll spacing by the base width would be five times. Thedrawing speed was at 300%/minute. After that, the film was allowed topass through the four cooling rolls where the roll temperaturedifferences were each set at 30 degrees Celsius lower with reference tothe drawing temperature, and was cooled gradually. During this time, thefilm tension was loosened 3% in the longitudinal direction. Drawingoperation was conducted so that a predetermined magnification would bereached under this condition.

The amount of residual solvent was calculated according to the followingformula:Amount of residual solvent (percent by mass)=(M−N)/N×100

where M denotes the mass of the film immediately after separation, and Nindicates the mass of the separated film immediately after having beendried at 120 degrees Celsius for 30 minutes.

Substrate films mentioned below were prepared by changing the drawingmagnification under a drawing condition similar to the above, as long asthere is no notice especially.

<How to Produce the Substrate Film 102 of the Present Invention>

The dope A was cast using a band caster. When the amount of residualsolvent had reached 60%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 20% in the TD direction andthen 20% in the MD direction. After that, it was dried at 120 degreesCelsius to get the substrate film 102 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 103 of the Present Invention>

The dope A was cast using a band caster. When the amount of residualsolvent had reached 70%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 30% in the TD direction andthen 30% in the MD direction. After that, it was dried at 120 degreesCelsius to get the substrate film 103 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 104 of the Present Invention>

The dope A was made to contain 0.1 percent by mass of EPEG(ethylphthalylethylglycolate) as a plasticizer. The resulting dope wascast using a band caster. When the amount of residual solvent hadreached 70%, it was separated from the band and was fed to the tenterimmediately, where it was drawn 30% in the TD direction and then 30% inthe MD direction. After that, it was dried at 120 degrees Celsius to getthe substrate film 104 of the present invention. Casting was made insuch a way as to ensure that the film thickness would be 100 μm in thefinal stage.

<How to Produce the Substrate Film 105 of the Present Invention>

The dope A was made to contain 0.5 percent by mass of EPEG(ethylphthalylethylglycolate) as a plasticizer. The resulting dope wascast using a band caster. When the amount of residual solvent hadreached 70%, it was separated from the band and was fed to the tenterimmediately, where it was drawn 30% in the TD direction and then 30% inthe MD direction. After that, it was dried at 120 degrees Celsius to getthe substrate film 105 of the present invention. Coating was made insuch a way as to ensure that the film thickness would be 100 μm in thefinal stage.

<How to Produce the Substrate Film 106 for Comparison>

The dope A was made to contain 1.0 percent by mass of EPEG(ethylphthalylethylglycolate) as a plasticizer. The resulting dope wascast using a band caster. When the amount of residual solvent hadreached 70%, it was separated from the band and was fed to the tenterimmediately, where it was drawn 30% in the TD direction and then 30% inthe MD direction. After that, it was dried at 120 degrees Celsius to getthe substrate film 106 of the present invention. Coating was made insuch a way as to ensure that the film thickness would be 100 μm in thefinal stage.

<How to Produce the Substrate Film 107 of the Present Invention>

60 parts by mass of ethanol, 685 parts by mass of methylene chloride and100 parts by mass of triacetyl cellulose (hereinafter referred to as“TAC”) were put in a mixing tank. They were dissolved while being heatedand stirred at 80 degrees Celsius to yield dope B.

This dope was cast using a band caster. When the amount of residualsolvent had reached 50%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 10% in the TD direction andthen 10% in the MD direction. After that, it was dried at 120 degreesCelsius to get the substrate film 107 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 108 of the Present Invention>

The dope B was cast using a band caster. When the amount of residualsolvent had reached 60%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 20% in the TD direction andthen 20% in the MD direction. After that, it was dried at 120 degreesCelsius to get the substrate film 108 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 109 of the Present Invention>

The dope A was cast using a band caster. When the amount of residualsolvent had reached 70%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 30% in the TD direction andthen 30% in the MD direction. After that, it was dried at 120 degreesCelsius to get the substrate film 109 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 110 of the Present Invention>

Dope A was prepared in advance and was put in the mixing tank.

25.2 parts by mass of tetramethoxysilane, 12.6 parts by mass of ethanol,12.6 parts by mass of methylene chloride and 12 parts by mass of 0.5%aqueous solution of nitric acid were put in that order in another mixingtank. They were stirred at 120 degrees Celsius for one hour to yielddope C.

This dope C was mixed with dope A, and was stirred for one hour to yielddope D. The amount used for mixing was such that the mass ratio betweenthe DAC and SiO₂ in the dope A would be 91 to 9, assuming that all theadded tetramethoxysilane had changed into SiO₂. The resulting dope D wascast using a band caster. When the amount of residual solvent hadreached 50%, it was separated from the band and was fed to the tenterimmediately, where it was drawn 10% in the TD direction and then 10% inthe MD direction. After that, it was dried at 120 degrees Celsius to getthe substrate film 110 of the present invention. Casting was made insuch a way as to ensure that the film thickness would be 100 μm in thefinal stage.

<How to Produce the Substrate Film 111 of the Present Invention>

The dope D was cast using a band caster. When the amount of residualsolvent had reached 60%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 20% in the TD direction andthen 20% in the MD direction. After that, it was dried at 120 degreesCelsius to get the substrate film 111 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 112 of the Present Invention>

60 parts by mass of ethanol, 685 parts by mass of methylene chloride and100 parts by mass of the cellulose ester 1 yielded in the synthesisexample 1 were put in a mixing tank. They were dissolved by being heatedand stirred at 120 degrees Celsius to yield dope E.

In the similar manner, dope C was prepared in advance and was put inanother mixing tank. This dope E was mixed with dope C, and was stirredfor one hour to yield dope F.

The dope F was cast using a band caster. When the amount of residualsolvent had reached 50%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 10% in the TD direction andthen 10% in the MD direction. After that, it was dried at 120 degreesCelsius to get the substrate film 112 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 113 of the Present Invention>

The dope F was cast using a band caster. When the amount of residualsolvent had reached 60%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 20% in the TD direction andthen 20% in the MD direction. After that, it was dried at 120 degreesCelsius to get the substrate film 113 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 114 of the Present Invention>

60 parts by mass of ethanol, 685 parts by mass of methylene chloride, 0parts by mass of Coronate L (by Nippon Polyurethane Co., Ltd.) and 10parts by mass of DAC were put in a mixing tank. They were dissolved bybeing heated and stirred at 40 degrees Celsius to yield dope G.

This dope was cast using a band caster. When the amount of residualsolvent had reached 50%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 10% in the TD direction andthen 10% in the MD direction. After that, it was dried at 150 degreesCelsius to get the substrate film 114 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 115 of the Present Invention>

The dope G was cast using a band caster. When the amount of residualsolvent had reached 60%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 20% in the TD direction andthen 20% in the MD direction. After that, it was dried at 150 degreesCelsius to get the substrate film 115 of the present invention. Castingwas made in such a way as to ensure that the film thickness would be 100μm in the final stage.

<How to Produce the Substrate Film 116 of the Present Invention>

60 parts by mass of ethanol, 685 parts by mass of methylene chloride, 30parts, by mass of dipentaerithritol pentaacrylate (compound example 35),30 parts by mass of 1-hydroxycyclohexylphenylketone and 100 parts bymass of DAC were put in a mixing tank. They were dissolved by beingheated and stirred at 80 degrees Celsius to yield dope H.

This dope was cast using a band caster. When the amount of residualsolvent had reached 50%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 20% in the TD direction andthen 20% in the MD direction. After that, when the amount of residualsolvent had reached the level of 3% or less, ultraviolet rays of 200mW/cm² were applied to both surfaces of the film for ten seconds each,using a metal halide lamp. It was dried at 120 degrees Celsius to getthe substrate film 116 of the present invention. Casting was made insuch a way as to ensure that the film thickness would be 100 μm in thefinal stage.

<How to Produce the Substrate Film 117 of the Present Invention>

The dope H was cast using a band caster. When the amount of residualsolvent had reached 50%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 30% in the TD direction andthen 30% in the MD direction. After that, when the amount of residualsolvent had reached the level of 3% or less, ultraviolet rays of 200mW/cm² were applied to both surfaces of the film for ten seconds each,using a metal halide lamp. It was dried at 120 degrees Celsius to getthe film 117 of the present invention. Casting was made in such a way asto ensure that the film thickness would be 100 μm in the final stage.

<How to Produce the Substrate Film 118 of the Present Invention>

The dope H was cast using a band caster. When the amount of residualsolvent had reached 70%, it was separated from the band and was fed tothe tenter immediately, where it was drawn 50% in the TD direction andthen 50% in the MD direction. After that, when the amount of residualsolvent had reached the level of 3% or less, ultraviolet rays of 200mW/cm² were applied to both surfaces of the film for ten seconds each,using a metal halide lamp. It was dried at 120 degrees Celsius to getthe film 118 of the present invention. Casting was made in such a way asto ensure that the film thickness would be 100 μm in the final stage.

<How to Produce the Substrate Film 119 of the Present Invention>

The same dope A as that used in producing the substrate film 101 wasprepared. This dope was cast using a band caster. When the amount ofresidual solvent had reached 50%, it was separated from the band, andwas dried at 120 degrees Celsius without being drawn, whereby the film119 of the present invention was produced. Casting was made in such away as to ensure that the film thickness would be 100 μm in the finalstage.

<How to Produce the Substrate Film 120 of Comparative Example>

The same dope B as that used in producing the substrate film 107 wasprepared. This dope was cast using a band caster. When the amount ofresidual solvent had reached 50%, it was separated from the band, andwas dried at 120 degrees Celsius without being drawn, whereby the film120 of the present invention was produced. Casting was made in such away as to ensure that the film thickness would be 100 μm in the finalstage.

<Substrate Film 121 of Comparative Example>

The “SUMILITE FS-1300” by Sumitomo Bakelite as a polyether sulfone filmhaving a thickness of 100 μm was used as a substrate film 121 forcomparison.

<Substrate Film 122 of Comparative Example>

The “Pure Ace” by Teijin Limited as polycarbonate film having athickness of 100 μm was used as a substrate film 122 for comparison.

<Substrate Film 123 of Comparative Example>

The “Artone” by JSR as a polynorbornene film having a thickness of 100μm was used as a substrate film 123 for comparison.

The substrate films 101 through 118 produced in the aforementionedprocedure and the substrate films 119 through 123 as comparativeexamples were evaluated according to the following criteria. The resultsof evaluation are given in Table 1.

<<Measurement of Glass-Transition Temperature and Linear ExpansionCoefficient>>

The glass-transition temperature of the cellulose esters of the presentinvention cannot be measured accurately by a differential scanningcalorimeter (DSC) in many cases. Accordingly, the point of inflection ofthe temperature strain curve in the thermal mechanical analysis (TMA)was assumed as the glass-transition temperature.

The TMA-SS6100 by Seiko Instrument was used to measure the thermalstress and strain. A sample with a film thickness of 100 μm and a widthof 4 mm was clamped at a chuck distance of 20 mm, and The temperaturewas raised from room temperature up to 180 degrees Celsius to removeresidual the strain. Then it was raised from room temperature to 250degrees Celsius at 5 degrees Celsius per minute. The linear expansioncoefficient calculated from the elongation of the chuck distance. Thelinear expansion coefficient in the Table has only one value. Almost thesame linear expansion coefficient was obtained in both the MD and TDdirections.

As described above, the glass-transition temperature was calculated fromthe point of inflection of the temperature/strain curve.

<<Waveform Dispersion Characteristic of Birefringence>>

The automatic birefringence meter KOBRA-21ADH by Oji Keisokukiki Co.,Ltd. was used to measure the waveform dispersion characteristic ofbirefringence. The birefringence (nm) refers to the value obtained bymultiplying the difference in refractive indexes of the inner surface ofeach substrate film in the X and Y directions by 50 μm as an assumedthickness.

In the similar manner, the retardation value R₀ (480) and at 480 nm andretardation value R₀ (590) and at 590 nm were measured using theKOBRA-21ADH. The ratio between the birefringence value at 480 nm andthat at 560 nm was calculated as shown in the following formula toevaluate the waveform dispersion of the birefringence.P=R ₀(480)/R ₀(590)

<Measurement of Full-Light Transmittance>>

The Turbidity Meter T-2600DA by Tokyo Denshoku Co., Ltd. was used tomeasure the full-light transmittance. TABLE 1 Substrate film compositionTg *1 Cellulose ester Additive *2 *3 *4 (° C.) *5 P Remarks 101DAC(100%) — 10 93.3 2.2 203 49 0.97 Inv. 102 DAC(100%) — 20 93.3 3.3 20336 0.97 Inv. 103 DAC(100%) — 30 93.3 4.8 203 27 0.97 Inv. 104 DAC(100%)EPEG(0.1%) 30 92.4 4.8 200 30 0.97 Inv. 105 DAC(100%) EPEG(0.5%) 30 92.44.8 195 35 0.97 Inv. 106 DAC(100%) EPEG(1.0%) 30 92.4 4.8 178 61 0.97Comp. 107 TAC(100%) — 10 93.3 1.2 193 47 0.98 Inv. 108 TAC(100%) — 2093.3 2.5 193 34 0.98 Inv. 109 TAC(100%) — 30 92.2 3.2 193 25 0.98 Inv.110 DAC(91%) SiO₂(9%) 10 92.2 3.2 225 49 0.98 Inv. 111 DAC(91%) SiO₂(9%)20 92.2 4.2 225 36 0.98 Inv. 112 Cellulose SiO₂(9%) 10 92.2 3.2 217 500.99 Inv. ester 1(91%) 113 Cellulose SiO₂(9%) 20 92.2 3.2 217 42 0.99Inv. ester 1(91%) 114 DAC(91%) CORONATE L(9%) 10 92.2 3.2 206 46 0.98Inv. 115 DAC(91%) CORONATE L(9%) 20 92.2 3.2 206 38 0.98 Inv. 116DAC(77%) Compound 20 92.2 1.7 235 48 0.98 Inv. example 35(23%) 117DAC(77%) Compound 30 92.2 3.8 235 34 0.98 Inv. example 35(23%) 118DAC(77%) Compound 50 92.2 7.1 235 18 0.98 Inv. example 35(23%) 119DAC(100%) — 0 93.3 1.3 203 66 0.97 Comp. 120 TAC(100%) — 0 93.3 0.2 20355 0.98 Comp. 121 SUMILITE FS-1300 — 0 90.6 8.3 223 82 1.14 Comp. 122PURE ACE — 0 91.0 131 152 86 1.09 Comp. 123 ARTONE — 0 92.2 8.0 171 1021.01 Comp.*1: Substrate film No.,*2: Drawing magnification (%),*3: Full light transmittance (%),*4: Birefringence (Inner surface) (nm),*5: Linear expansion coefficient (ppm/° C.)Inv.: Invention,Comp.: Comparative exampleCompound example 35: dipenta-erithritol pentaacrylateEPEG; ethyl phthalyl ethyl glycolate (plasticizer)

The substrate films 122 and 123 of the comparative examples had a lowglass-transition temperature and a high linear expansion coefficient,and therefore, they are preferably used. The substrate film 121 has ahigh glass-transition temperature and high linear expansion coefficient;this was not preferable. The substrate films 119 and 120 of thecomparative examples had a high glass-transition temperature and a highlinear expansion coefficient; this was not preferable.

By contrast, although the composition was the same as that of the film119 of the comparative example, the substrate film 101 of the presentinvention having been subjected to the step of drawing maintained a highglass-transition temperature and a small linear expansion coefficient,and therefore, was a preferable film. Further, the substrate films 110and 111 with the increased draw magnification had a lower linearexpansion coefficient and were preferable.

The substrate films 110 and 111 composed of the DAC hybridized withsilica had the same linear expansion coefficient as that of the filmwithout silica used for hybridization, but there was a substantialimprovement of the Tg, and therefore, the substrate films 110 and 111were preferable. Further, the hybrid films 112 and 113 hybridized withthe cellulose ester having a site for silane coupling thereon had a highTg and low linear expansion coefficient, and therefore, were preferable.

The films 114 and 115 cross-linked with DAC using the cross-linkingagent had a high Tg and a low linear expansion coefficient, andtherefore, were preferable.

The substrate films 116 through 118 having a semi-IPN structure composedof the DAC and cross-linked acrylate polymer had high Tg and a lowlinear expansion coefficient, and therefore, were preferable.

Embodiment 2

Transparent conductive films 201 through 223 were prepared by formingthin films on the substrate films 101 through 123 obtained in the firstembodiment in the order of the clear hard coated layer (on bothsurfaces), moisture proof film (on both surfaces) and transparentconductive film (on one surface).

<Formation of a Clear Hard Coated Layer>

The substrate film 101 was coated using an extrusion coater so that thecomposition of the coating of the following hard coated layer would havea film thickness of 3 μm. After that, it was dried for one minute by thedrier with its temperature set at 80 degrees Celsius, and was thenexposed to ultraviolet irradiation of 120 mW/cm², whereby the clear hardcoated layer was formed. (Coating composition of clear hard coatedlayer) Dipenta-erithritol hexaacrylate monomer: 60 parts by massDipenta-erithritol hexaacrylate dimmer: 20 parts by massDipenta-erithritol hexaacrylate trimer: 20 parts by massDimethoxybenzophenone: 4 parts by mass Ethyl acetate: 50 parts by massMethylethyl ketone: 50 parts by mass Isopropyl alcohol: 50 parts by mass

<Formation of a Moisture Proof Film>

The plasma discharge apparatus equipped with parallel flat typeelectrodes was used. The aforementioned substrate film was placedbetween these electrodes, and a gas mixture was introduced therein,whereby a thin film was formed.

The following electrode was used: An alumina sprayed film of highdensity and high degree of adhesion was coated on a stainless steelplate having dimensions of 200 mm×200 mm×2 mm. Then a solvent made oftetramethoxysilane diluted with ethyl acetate was coated and dried.After that, it was exposed to ultraviolet irradiation and was cured. Itwas provided with pore sealing treatment. Further, the surface of thedielectric coated in the aforementioned manner was made flat by grindingand was processed so as to yield a Rmax of 5 μm. The electrode wasformed in this manner and was grounded.

To produce an application electrode, a plurality of hollow rectangulartitanium pipes coated with the aforementioned dielectric under the sameconditions were produced, whereby opposing electrode groups weremanufactured.

To provide power for plasma generation, the high-frequency power sourceJRF-10000 by Nippon Denshi Co., Ltd. was used to supply the electricityof the voltage having a frequency of 13.56 MHz and power of 5 W/cm², anda gas mixture of the following composition was introduced betweenelectrodes: Inert gas: Argon: 99.3 percent by volume Reactive gas 1:Hydrogen: 0.5 percent by volume Reactive gas 2: Tetraethoxysilane: 0.3percent by volume

Atmospheric plasma processing was carried out using the aforementionedreactive gas under the aforementioned reaction conditions, and a siliconoxide film having a film thickness of 180 nm was formed as a moistureproof film on the clear hard coated layer of the substrate films 101through 123 equipped with the clear hard coated layer.

<Formation of a Transparent Conductive Film>

A transparent conductive film was formed using the gas mixture havingthe following composition, under the same atmospheric plasma conditionsas those for formation of the moisture proof film except that the supplypower was changed to 12 W/cm²: Inert gas: Helium: 98.69 percent byvolume Reactive gas 1: Hydrogen: 0.05 percent by volume Reactive gas 2:Indium acetylacetonate: 1.2 percent by volume Reactive gas 3: Dibutyltin diacetate: 0.05 percent by volume Reactive gas 4: Tetraethoxysilane:0.01 percent by volume

Atmospheric plasma processing was carried out using the aforementionedreactive gas under the aforementioned reaction conditions, and atin-doped indium oxide film (ITO film) (having a thickness of 110 nm)was formed as a transparent conductive film on the silicon oxide layerof the substrate films 101 through 123 equipped with the clear hardcoated layer and silicon oxide layer, whereby transparent conductivefilms 201 through 223 were obtained.

The transparent conductive films 201 through 223 produced in theaforementioned manner were evaluated as follows:

<<Transmittance>>

The Turbidity Meter T-2600DA by Tokyo Denshoku Co., Ltd. was used tomeasure the transmittance.

<<Evaluation of Moisture Permeability>>

Moisture permeability was measured according to the conditions specifiedin JIS-Z-0208 (at 40 degrees Celsius with 90% RH). Further, a series ofcooling and heating cycle (thermal shock cycle) was conducted ten times,wherein a sample was heated at 180 degrees Celsius for one hour and wasthen left to cool at room temperature for one hour. After that, moisturepermeability was measured.

<<Specific Resistance>>

Specific resistance was obtained by the four-terminal techniqueaccording to the JIS-R-1637. The Lorester GP and MCP-T600 by MitsubishiChemical Co., Ltd. were used for measurement.

The specific resistance, transmittance and moisture permeability of thetransparent conductive films 201 through 223 were evaluated. The resultsof evaluation are given in Table 2. TABLE 2 Trans- Specific parentresistance conductive Transmit- (×10⁻⁴ film tance (%) *1 *2 Ω cm)Remarks 201 87 0.47 1.00 2.3 Invention 202 88 0.48 0.88 2.3 Invention203 88 0.48 0.71 2.2 Invention 204 88 0.48 0.79 2.2 Invention 205 880.48 0.97 2.3 Invention 206 88 0.45 * 2.8 Comparative example 207 880.43 0.93 2.7 Invention 208 88 0.43 0.83 2.7 Invention 209 88 0.43 0.812.8 Invention 210 88 0.51 0.91 1.7 Invention 211 88 0.52 0.83 1.7Invention 212 88 0.49 0.97 1.8 Invention 213 88 0.49 0.88 1.8 Invention214 88 0.41 0.95 1.9 Invention 215 88 0.41 0.89 1.9 Invention 216 880.34 0.96 1.7 Invention 217 88 0.33 0.83 1.7 Invention 218 88 0.33 0.691.7 Invention 219 88 0.48 2.48 2.3 Comparative example 220 88 0.43 1.432.7 Comparative example 221 85 0.33 6.4 1.9 Comparative example 222 850.3 * 2.6 Comparative example 223 87 0.31 * 2.5 Comparative example*1: Moisture permeability (immediate) (g/m²/d)*2: Moisture permeability (after thermal shock cycle) (g/m²/d)* Softening and deformation occurred to the films 219 and 220 duringthermal shock cycle and moisture permeability was unsuccessful.

Table 2 indicates that the moisture permeability of the substrate filmin the present invention and that in the comparative examples is reducedby the silicon oxide layer provided by the atmospheric pressure plasmaprocessing.

The substrate film of the present invention has a low linear expansioncoefficient, and therefore, deterioration of moisture permeability isreduced even after going through the thermal shock cycle, whereby anexcellent transparent conductive film is provided. In case of thetransparent conductive films 219 through 221 of comparative examples,the moisture permeability can be reduced by formation of a moistureproof layer. However, since the substrate films 119 through 121 as thesubstrates have a high linear expansion coefficient, the moisture prooflayer is cracked and the moisture permeability deteriorates due to theexpansion and shrinkage of the support member after goring through thethermal shock cycle. The transparent conductive films 222 and 223 aresubjected to deformation during the thermal shock cycle because the heatresistance of the substrate films 122 and 123 is low. This is notpreferred.

Atmospheric pressure plasma processing allows the transparent conductivefilms of high transmittance and low specific resistance to be formed onthe substrate films of the present invention and those of comparativeexamples.

Embodiment 3

A TN liquid crystal display device given in FIG. 4 was manufacturedaccording to the following procedure, using the aforementionedtransparent conductive films 201 through 205 and 207 through 218 of thepresent invention, and the transparent conductive films 206 and 219through 223 of comparative examples.

<How to Manufacture the TN Liquid Crystal Display Device>

A resin layer (not illustrated) for smoothing was coated on theaforementioned transparent conductive film as a transparent conductivesubstrate 401. A transparent conductive film was formed further on thisresin layer directly or via a silicon dioxide film. This was providedwith patterning to form a stripe-like shape, so that a display electrode402 was formed. An opposing substrate was produced using the sametransparent conductive substrate. Namely, a display electrode was formedon the opposing substrate side as well. Further, an oriented film 403and sealing material (not illustrated) were formed by a printing methodor the like. Two substrates were placed opposite to each other afterspraying with spacer, and a hollow cell was formed by pressure contact.A liquid crystal was introduced into this hollow cell by vacuuminjection, and the terminal portion was taken out so that the drivevoltage would not be applied to the opposing display electrodes. Then aliquid crystal display device was assembled by a combination of a phasedifference plate, deflecting plate, touch panel and light source (notillustrated).

In the liquid crystal display device manufactured in the aforementionedmethod, excellent images were provided by the transparent conductivefilms 201 through 205 and 207 through 218 of the present invention.However, image distortion and color misregistration were observed in thecase of the transparent conductive films 206 and 219 through 223 of thecomparative examples.

Embodiment 4

A simple matrix drive type organic electroluminescence display devicegiven in FIG. 5 was manufactured according to the following procedure,using the transparent conductive films 201 through 205 and 207 through218 of the present invention, and the transparent conductive films 206and 219 through 223 of the comparative examples.

<How to Manufacture the Organic Electroluminescence Display Device>

A transparent conductive film 502 (anode) was pattern on theaforementioned transparent conductive film as a transparent conductivesubstrate 501. After that, using the neutral detergent, acetone andethanol, the film was subjected to ultrasonic cleaning. The film wasthen pulled out of the boiled ethanol and was dried. After the surfaceof the transparent conductive film was subjected to UV/O₃ cleaning,N,N′-diphenyl-m-tolyl-4,4′-diamine-1,1′-biphenyl (TPD) was deposited toa thickness of 55 nm at a deposition rate of 0.2 nm per second using avacuum deposition apparatus, whereby a positive hole injection andtransport layer 503 was formed.

Further, Alq₃: tris(8-quinolinolate)aluminum was deposited to athickness of 50 nm at a deposition rate of 0.2 nm per second, whereby anelectron injection, transport and light emission layer 504 was formed.

Then a cathode film 505 was manufactured to a thickness of 200 nm by asputtering apparatus according to the DC sputter method, wherein theAl—Sm alloy (Sm: 10 at %) was used as a target. In this case, argon wasused as a sputter gas. The gas pressure was 3.5 Pa and the distancebetween the target and substrate (Ts) was 9.0 cm. The power supplied was1.2 W/cm².

In the final phase, SiO₂ was sputtered to a thickness of 200 nm to forma protective layer 506, thereby producing an organic electroluminescencedisplay device. This organic electroluminescence display device wascomposed of two parallel stripe-like cathodes and eight parallelstripe-like electrodes arranged orthogonal to each other, wherein 2×2 mmmatrix device units (pixels) are arranged at intervals of 2 mm to form a16-pixel device with a 8×2 matrix.

The organic electroluminescence display obtained in the aforementionedprocedure was driven at 9 volts. In the transparent conductive films 201through 205 and 207 through 218 of the embodiment, a luminance of 350cd/m² or more was produced. However, in the case of the transparentconductive films 206 and 219 through 223 of the comparative examples,the luminance was only 50 cd/m² or less. The required intensity of lightemission in an organic electroluminescence display device could not beachieved.

Embodiment 5

A touch panel given in FIG. 6 was manufactured according to thefollowing procedure, using the aforementioned transparent conductivefilms 201 through 205 and 207 through 218 of the present invention, andthe transparent conductive films 206 and 219 through 223 of comparativeexamples.

<How to Assemble the Touch Panel>

The touch panel glass ITO (sputtering film) was used as the lowerelectrode 606 shown in FIG. 6. The transparent conductive films 201through 205 and 207 through 218 of the present invention, and thetransparent conductive films 206 and 219 through 223 of comparativeexamples were used as the transparent conductive substrate 601 of theupper electrode 605. Transparent conductive film surfaces 603 and 604were arranged face to face with each other. Using the thermosetting typedot spacer 607, a panel was produced at intervals of 7 μm, whereby atouch panel was assembled.

An image was placed below the touch panel assembled in theaforementioned procedure. It was observed from an angle of 45 degrees,and a visibility test was conducted to check if the image viewed throughwas free from any distortion or not. This test revealed that the imagewas observed without any distortion in the case of the transparentconductive films 201 through 205 and 207 through 218 of the presentinvention. However, the image was distorted in the case of thetransparent conductive films 206 and 219 through 223 of comparativeexamples.

INDUSTRIAL APPLICABILITY

The present invention provides a transparent film for display substratesuch as a liquid crystal display, organic electroluminescence display ortouch panel characterized by low birefringence, positive waveformdispersion properties, high glass-transition temperature and a lowlinear expansion coefficient.

If a moisture proof film is provided on the transparent film for displaysubstrate of the present invention, the moisture permeability of thefilm can be reduced without adversely affecting the electronic devicesusing the substrate film.

A transparent conductive film of high transparency and low specificresistance can be coated on the transparent film for display substrateof the present invention provided with the moisture proof film.

If a moisture proof film and transparent conductive film provided on thetransparent film for display substrate of the present invention areformed by atmospheric pressure plasma processing, manufacture ofhigh-quality transparent conductive films with improved productivity isensured.

Thus, the present invention allows production of a high-quality liquidcrystal display, organic electroluminescence display and touch panel.

1. A transparent film for display substrate, containing: a celluloseester, and a plasticizer in an amount of less than 1 percent, whereinthe transparent film is drawn 3 through 100 percent both in a conveyancedirection and a lateral direction.
 2. The transparent film for displaysubstrate, described in claim 1, wherein the transparent film contains ahydrolyzed polycondensate of the cellulose ester and an alkoxysilaneexpressed by the following general formula (1):R₄—Si(OR′)_(n)   General formula (1) (where R and R′ represent ahydrogen atom or monovalent substituents independently, and n denotes 3or 4).
 3. The transparent film for display substrate, described in claim2, wherein the hydrolyzed hydrolyzed polycondensate of the celluloseester and the alkoxysilane expressed by the general formula (1) areexpressed by the following general formula (2), and a total amount of aninorganic high molecular compound expressed by the general formula (2)is less than 40 percent by mass in the transparent film:R_(4-n)SiO_(n/2)   General formula (2) (where R is synonymous with thatin said general formula (1)).
 4. The transparent film for displaysubstrate, described in, claim 1 wherein the transparent film containsan organic crosslinking agent having a plurality of any of an isocyanategroup, a thioisocyanate group and an acid hydride residue, in an amountof 1 through 20 percent by mass so that the cellulose ester iscrosslinked.
 5. The transparent film for display substrate, described inclaim 1 wherein the number average molecular mass of the cellulose esteris 100,000 or more.
 6. The transparent film for display substrate,described in claim 1 wherein the substituent of the cellulose estersatisfies the following formula (A) and (B):0≦Y≦1.5   Formula (A)1.0≦X+Y≦2.9   Formula (B) (wherein “X” denotes the degree ofsubstitution and “Y” indicates the degree of substitution by using asubstituent containing an alkoxysilyl group).
 7. The transparent filmfor display substrate, described in claim 1 wherein the degree ofsubstitution of said cellulose ester by the acetyl group is 2.2 throughless than 2.9.
 8. The transparent film for display substrate, describedin claim 1 wherein the transparent film contains a crosslinked polymerand the cellulose ester and the crosslinked polymer forms a semi-IPN(semi-interpenetrating polymer network) type polymer alloy.
 9. Thetransparent film for display substrate, described of claim 8, whereinthe transparent film contains the crosslinked polymer in an amount of 5through 50 percent by mass of the transparent film.
 10. The transparentfilm for display substrate, described in claim 1 wherein the transparentfilm is composed of a cellulose film of which glass-transitiontemperature obtained by thermal mechanical analysis (TMA) is 180 degreesCelsius or more, and the coefficients of linear expansion in both MD andTD directions are in the range from 5 through 50 ppm/degrees Celsius.11. The transparent film for display substrate, described in claim 1when the in-plane retardation value at the wavelength of 590 nm is R₀(590) and the in-plane retardation value at the wavelength of 480 nm isR₀ (480); the ratio [R₀(480)/R₀(590)] is not less than 0.8 through lessthan 1.0.
 12. A display substrate wherein a moisture proof filmcontaining a metal oxide or metal nitride is formed on at least one ofthe surfaces of a transparent film for display substrate in claim 1 anda transparent conductive film is formed on the moisture proof film or onthe surface opposite to the surface where the moisture proof film isformed.
 13. The display substrate of claim 12, wherein said moistureproof film is mainly composed of silicon oxide.
 14. The displaysubstrate of claim 12, wherein the moisture proof film and thetransparent conductive film is formed by applying a high frequencyvoltage between opposed electrodes under atmospheric pressure or underapproximately atmospheric pressure for a discharge, generating areactive gas in the plasma state by the discharge, exposing thetransparent film for display substrate to the reactive gas in the plasmastate whereby the moisture proof film and the transparent conductivefilm are formed on the transparent film.
 15. A liquid crystal displayusing the display substrate in. claim 12
 16. An organicelectroluminescence display using the display substrate in any one of.claim 12
 17. A touch panel using the display substrate in any one of.claim 12
 18. A method for manufacturing a transparent film for displaysubstrate according to a casting film forming method, comprising thesteps of: casting the dope containing a cellulose ester and aplasticizer in an amount of less than 1 percent, onto a casting supportmember to form a web; drawing the web 3 through 100 percent both in theconveyance direction and the width direction; and drying the web.
 19. Amethod for manufacturing a display substrate comprising the steps of:applying a high frequency voltage between opposed electrodes underatmospheric pressure or under approximately atmospheric pressure for adischarge, generating a reactive gas in the plasma state by thedischarge, exposing the transparent film for display substrate formed bythe method of claim 18 to the reactive gas in the plasma state wherebythe moisture proof film and the transparent conductive film are formedon the transparent film.
 20. The method for manufacturing a displaysubstrate of claim 19, wherein the frequency of the high frequencyvoltage is in the range from 100 kHz through 2.5 GHz, and the supplypower is in the range from 1 W/cm² through 50 W/cm².
 21. The method formanufacturing a display substrate of claim 20, wherein the frequency ofsaid high frequency voltage is in the range from 100 kHz through 150MHz.